Also no plugin required

Credits/Author: @Klas Karlsson and an extension to @Matthias Kuhn's answer.

No plugin required

Credits/Author: @Klas Karlsson and an extension to @Matthias Kuhn's answer.

Also no plugin required

1. Plugins > Python Console > Show Editor
2. Copy&Paste the code below into a new Python file and press Run

"""
This script should be run from the Python consol inside QGIS.

It adds online sources to the QGIS Browser.
Each source should contain a list with the folowing items (string type):
[sourcetype, title, authconfig, password, referer, url, username, zmax, zmin]

You can add or remove sources from the sources section of the code.

Script by Klas Karlsson
Sources from https://qms.nextgis.com/

Licence GPL-3

Regarding the terms of use for these background maps YOU will need to verify that you
follow the individual EULA that comes with the different services,
Most likely they will restrict how you can use the data.
"""

# Sources
sources = []
sources.append(["connections-xyz","Google Maps","","","","https://mt1.google.com/vt/lyrs=m&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D","","19","0"])
sources.append(["connections-xyz","Google Satellite", "", "", "", "https://mt1.google.com/vt/lyrs=s&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D", "", "19", "0"])
sources.append(["connections-xyz","Google Terrain", "", "", "", "https://mt1.google.com/vt/lyrs=t&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D", "", "19", "0"])
sources.append(["connections-xyz","Google Terrain Hybrid", "", "", "", "https://mt1.google.com/vt/lyrs=p&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D", "", "19", "0"])
sources.append(["connections-xyz","Google Satellite Hybrid", "", "", "", "https://mt1.google.com/vt/lyrs=y&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D", "", "19", "0"])
sources.append(["connections-xyz","Stamen Terrain", "", "", "Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL", "http://tile.stamen.com/terrain/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","Stamen Toner", "", "", "Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL", "http://tile.stamen.com/toner/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","Stamen Toner Light", "", "", "Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL", "http://tile.stamen.com/toner-lite/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","Stamen Watercolor", "", "", "Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL", "http://tile.stamen.com/watercolor/%7Bz%7D/%7Bx%7D/%7By%7D.jpg", "", "18", "0"])
sources.append(["connections-xyz","Wikimedia Map", "", "", "OpenStreetMap contributors, under ODbL", "https://maps.wikimedia.org/osm-intl/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "1"])
sources.append(["connections-xyz","Wikimedia Hike Bike Map", "", "", "OpenStreetMap contributors, under ODbL", "http://tiles.wmflabs.org/hikebike/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "17", "1"])
sources.append(["connections-xyz","Esri Boundaries Places", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/Reference/World_Boundaries_and_Places/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "20", "0"])
sources.append(["connections-xyz","Esri Gray (dark)", "", "", "", "http://services.arcgisonline.com/ArcGIS/rest/services/Canvas/World_Dark_Gray_Base/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "16", "0"])
sources.append(["connections-xyz","Esri Gray (light)", "", "", "", "http://services.arcgisonline.com/ArcGIS/rest/services/Canvas/World_Light_Gray_Base/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "16", "0"])
sources.append(["connections-xyz","Esri National Geographic", "", "", "", "http://services.arcgisonline.com/ArcGIS/rest/services/NatGeo_World_Map/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "12", "0"])
sources.append(["connections-xyz","Esri Ocean", "", "", "", "https://services.arcgisonline.com/ArcGIS/rest/services/Ocean/World_Ocean_Base/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "10", "0"])
sources.append(["connections-xyz","Esri Satellite", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "17", "0"])
sources.append(["connections-xyz","Esri Standard", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "17", "0"])
sources.append(["connections-xyz","Esri Terrain", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/World_Terrain_Base/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "13", "0"])
sources.append(["connections-xyz","Esri Transportation", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/Reference/World_Transportation/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "20", "0"])
sources.append(["connections-xyz","Esri Topo World", "", "", "", "http://services.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "20", "0"])
sources.append(["connections-xyz","OpenStreetMap Standard", "", "", "OpenStreetMap contributors, CC-BY-SA", "http://tile.openstreetmap.org/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "19", "0"])
sources.append(["connections-xyz","OpenStreetMap H.O.T.", "", "", "OpenStreetMap contributors, CC-BY-SA", "http://tile.openstreetmap.fr/hot/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "19", "0"])
sources.append(["connections-xyz","OpenStreetMap Monochrome", "", "", "OpenStreetMap contributors, CC-BY-SA", "http://tiles.wmflabs.org/bw-mapnik/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "19", "0"])
sources.append(["connections-xyz","OpenTopoMap", "", "", "Kartendaten: © OpenStreetMap-Mitwirkende, SRTM | Kartendarstellung: © OpenTopoMap (CC-BY-SA)", "https://tile.opentopomap.org/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "17", "1"])
sources.append(["connections-xyz","Strava All", "", "", "OpenStreetMap contributors, CC-BY-SA", "https://heatmap-external-b.strava.com/tiles/all/bluered/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "15", "0"])
sources.append(["connections-xyz","Strava Run", "", "", "OpenStreetMap contributors, CC-BY-SA", "https://heatmap-external-b.strava.com/tiles/run/bluered/%7Bz%7D/%7Bx%7D/%7By%7D.png?v=19", "", "15", "0"])
sources.append(["connections-xyz","Open Weather Map Temperature", "", "", "Map tiles by OpenWeatherMap, under CC BY-SA 4.0", "http://tile.openweathermap.org/map/temp_new/%7Bz%7D/%7Bx%7D/%7By%7D.png?APPID=1c3e4ef8e25596946ee1f3846b53218a", "", "19", "0"])
sources.append(["connections-xyz","Open Weather Map Clouds", "", "", "Map tiles by OpenWeatherMap, under CC BY-SA 4.0", "http://tile.openweathermap.org/map/clouds_new/%7Bz%7D/%7Bx%7D/%7By%7D.png?APPID=ef3c5137f6c31db50c4c6f1ce4e7e9dd", "", "19", "0"])
sources.append(["connections-xyz","Open Weather Map Wind Speed", "", "", "Map tiles by OpenWeatherMap, under CC BY-SA 4.0", "http://tile.openweathermap.org/map/wind_new/%7Bz%7D/%7Bx%7D/%7By%7D.png?APPID=f9d0069aa69438d52276ae25c1ee9893", "", "19", "0"])
sources.append(["connections-xyz","CartoDb Dark Matter", "", "", "Map tiles by CartoDB, under CC BY 3.0. Data by OpenStreetMap, under ODbL.", "http://basemaps.cartocdn.com/dark_all/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","CartoDb Positron", "", "", "Map tiles by CartoDB, under CC BY 3.0. Data by OpenStreetMap, under ODbL.", "http://basemaps.cartocdn.com/light_all/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","Bing VirtualEarth", "", "", "", "http://ecn.t3.tiles.virtualearth.net/tiles/a{q}.jpeg?g=1", "", "19", "1"])

 
# Add sources to browser
for source in sources:
   connectionType = source[0]
   connectionName = source[1]
   QSettings().setValue("qgis/%s/%s/authcfg" % (connectionType, connectionName), source[2])
   QSettings().setValue("qgis/%s/%s/password" % (connectionType, connectionName), source[3])
   QSettings().setValue("qgis/%s/%s/referer" % (connectionType, connectionName), source[4])
   QSettings().setValue("qgis/%s/%s/url" % (connectionType, connectionName), source[5])
   QSettings().setValue("qgis/%s/%s/username" % (connectionType, connectionName), source[6])
   QSettings().setValue("qgis/%s/%s/zmax" % (connectionType, connectionName), source[7])
   QSettings().setValue("qgis/%s/%s/zmin" % (connectionType, connectionName), source[8])

# Update GUI
iface.reloadConnections()

3. After code executes a list of basemaps will appear under the XYZ Tiles in the Browser panel, see image below.

1. Plugins > Python Console > Show Editor
2. Copy&Paste the code below into a new Python file and press Run script

"""
This script should be run from the Python consol inside QGIS.

It adds online sources to the QGIS Browser.
Each source should contain a list with the folowing items (string type):
[sourcetype, title, authconfig, password, referer, url, username, zmax, zmin]

You can add or remove sources from the sources section of the code.

Script by Klas Karlsson
Sources from https://qms.nextgis.com/

Licence GPL-3

Regarding the terms of use for these background maps YOU will need to verify that you
follow the individual EULA that comes with the different services,
Most likely they will restrict how you can use the data.
"""

# Sources
sources = []
sources.append(["connections-xyz","Google Maps","","","","https://mt1.google.com/vt/lyrs=m&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D","","19","0"])
sources.append(["connections-xyz","Google Satellite", "", "", "", "https://mt1.google.com/vt/lyrs=s&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D", "", "19", "0"])
sources.append(["connections-xyz","Google Terrain", "", "", "", "https://mt1.google.com/vt/lyrs=t&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D", "", "19", "0"])
sources.append(["connections-xyz","Google Terrain Hybrid", "", "", "", "https://mt1.google.com/vt/lyrs=p&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D", "", "19", "0"])
sources.append(["connections-xyz","Google Satellite Hybrid", "", "", "", "https://mt1.google.com/vt/lyrs=y&x=%7Bx%7D&y=%7By%7D&z=%7Bz%7D", "", "19", "0"])
sources.append(["connections-xyz","Stamen Terrain", "", "", "Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL", "http://tile.stamen.com/terrain/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","Stamen Toner", "", "", "Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL", "http://tile.stamen.com/toner/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","Stamen Toner Light", "", "", "Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL", "http://tile.stamen.com/toner-lite/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","Stamen Watercolor", "", "", "Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL", "http://tile.stamen.com/watercolor/%7Bz%7D/%7Bx%7D/%7By%7D.jpg", "", "18", "0"])
sources.append(["connections-xyz","Wikimedia Map", "", "", "OpenStreetMap contributors, under ODbL", "https://maps.wikimedia.org/osm-intl/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "1"])
sources.append(["connections-xyz","Wikimedia Hike Bike Map", "", "", "OpenStreetMap contributors, under ODbL", "http://tiles.wmflabs.org/hikebike/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "17", "1"])
sources.append(["connections-xyz","Esri Boundaries Places", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/Reference/World_Boundaries_and_Places/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "20", "0"])
sources.append(["connections-xyz","Esri Gray (dark)", "", "", "", "http://services.arcgisonline.com/ArcGIS/rest/services/Canvas/World_Dark_Gray_Base/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "16", "0"])
sources.append(["connections-xyz","Esri Gray (light)", "", "", "", "http://services.arcgisonline.com/ArcGIS/rest/services/Canvas/World_Light_Gray_Base/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "16", "0"])
sources.append(["connections-xyz","Esri National Geographic", "", "", "", "http://services.arcgisonline.com/ArcGIS/rest/services/NatGeo_World_Map/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "12", "0"])
sources.append(["connections-xyz","Esri Ocean", "", "", "", "https://services.arcgisonline.com/ArcGIS/rest/services/Ocean/World_Ocean_Base/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "10", "0"])
sources.append(["connections-xyz","Esri Satellite", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "17", "0"])
sources.append(["connections-xyz","Esri Standard", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "17", "0"])
sources.append(["connections-xyz","Esri Terrain", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/World_Terrain_Base/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "13", "0"])
sources.append(["connections-xyz","Esri Transportation", "", "", "", "https://server.arcgisonline.com/ArcGIS/rest/services/Reference/World_Transportation/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "20", "0"])
sources.append(["connections-xyz","Esri Topo World", "", "", "", "http://services.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer/tile/%7Bz%7D/%7By%7D/%7Bx%7D", "", "20", "0"])
sources.append(["connections-xyz","OpenStreetMap Standard", "", "", "OpenStreetMap contributors, CC-BY-SA", "http://tile.openstreetmap.org/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "19", "0"])
sources.append(["connections-xyz","OpenStreetMap H.O.T.", "", "", "OpenStreetMap contributors, CC-BY-SA", "http://tile.openstreetmap.fr/hot/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "19", "0"])
sources.append(["connections-xyz","OpenStreetMap Monochrome", "", "", "OpenStreetMap contributors, CC-BY-SA", "http://tiles.wmflabs.org/bw-mapnik/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "19", "0"])
sources.append(["connections-xyz","OpenTopoMap", "", "", "Kartendaten: © OpenStreetMap-Mitwirkende, SRTM | Kartendarstellung: © OpenTopoMap (CC-BY-SA)", "https://tile.opentopomap.org/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "17", "1"])
sources.append(["connections-xyz","Strava All", "", "", "OpenStreetMap contributors, CC-BY-SA", "https://heatmap-external-b.strava.com/tiles/all/bluered/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "15", "0"])
sources.append(["connections-xyz","Strava Run", "", "", "OpenStreetMap contributors, CC-BY-SA", "https://heatmap-external-b.strava.com/tiles/run/bluered/%7Bz%7D/%7Bx%7D/%7By%7D.png?v=19", "", "15", "0"])
sources.append(["connections-xyz","Open Weather Map Temperature", "", "", "Map tiles by OpenWeatherMap, under CC BY-SA 4.0", "http://tile.openweathermap.org/map/temp_new/%7Bz%7D/%7Bx%7D/%7By%7D.png?APPID=1c3e4ef8e25596946ee1f3846b53218a", "", "19", "0"])
sources.append(["connections-xyz","Open Weather Map Clouds", "", "", "Map tiles by OpenWeatherMap, under CC BY-SA 4.0", "http://tile.openweathermap.org/map/clouds_new/%7Bz%7D/%7Bx%7D/%7By%7D.png?APPID=ef3c5137f6c31db50c4c6f1ce4e7e9dd", "", "19", "0"])
sources.append(["connections-xyz","Open Weather Map Wind Speed", "", "", "Map tiles by OpenWeatherMap, under CC BY-SA 4.0", "http://tile.openweathermap.org/map/wind_new/%7Bz%7D/%7Bx%7D/%7By%7D.png?APPID=f9d0069aa69438d52276ae25c1ee9893", "", "19", "0"])
sources.append(["connections-xyz","CartoDb Dark Matter", "", "", "Map tiles by CartoDB, under CC BY 3.0. Data by OpenStreetMap, under ODbL.", "http://basemaps.cartocdn.com/dark_all/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","CartoDb Positron", "", "", "Map tiles by CartoDB, under CC BY 3.0. Data by OpenStreetMap, under ODbL.", "http://basemaps.cartocdn.com/light_all/%7Bz%7D/%7Bx%7D/%7By%7D.png", "", "20", "0"])
sources.append(["connections-xyz","Bing VirtualEarth", "", "", "", "http://ecn.t3.tiles.virtualearth.net/tiles/a{q}.jpeg?g=1", "", "19", "1"])

# Add sources to browser
for source in sources:
   connectionType = source[0]
   connectionName = source[1]
   QSettings().setValue("qgis/%s/%s/authcfg" % (connectionType, connectionName), source[2])
   QSettings().setValue("qgis/%s/%s/password" % (connectionType, connectionName), source[3])
   QSettings().setValue("qgis/%s/%s/referer" % (connectionType, connectionName), source[4])
   QSettings().setValue("qgis/%s/%s/url" % (connectionType, connectionName), source[5])
   QSettings().setValue("qgis/%s/%s/username" % (connectionType, connectionName), source[6])
   QSettings().setValue("qgis/%s/%s/zmax" % (connectionType, connectionName), source[7])
   QSettings().setValue("qgis/%s/%s/zmin" % (connectionType, connectionName), source[8])

# Update GUI
iface.reloadConnections()

3. After code executes a list of basemaps will appear under the XYZ Tiles in the Browser panel, see image below.