To solve the problem, right click your basemap layer and set CRS back to
EPSG:3857 - the initial one and the only one valid. Do not change layer CRS: See here for details: https://gis.stackexchange.com/a/392388/88814 and https://gis.stackexchange.com/a/383437/88814.
You can also get lat/lon (
EPSG:4326) coordinates even if you have another project CRS (e.g.
EPSG:3857 to show an undistorted OSM basemap) by right-clicking on the map canvas and selecting
WGS84: see second screenshot below.
The coordinates that you get are in
EPSG:3857 (WebMercator - used for the OpenStreetMap basemap). To get lat/lon coordinates (the one you want), project CRS should be in WGS84 (
That is the case in your screenshot. However, with
EPSG:4326, the OSM map should look heavily distorted - as on my first screenshot below, but with the correct lat/lon values for coordinates.
Your basemap seems to be undistorted, what is not possible if it is "warped" from it's initial
EPSG:3857 (WebMercator, used for most online maps) to the project's
EPSG:4326. You (unintentionally) "un-distorted" the basemap by assigning layer CRS
EPSG:4326 - it looks undistorted, but like this, places on the OSM basemap are misplaced. You "streched" the OSM map to a very huge extent that goes much beyond the min/max extent for
EPSG:4326, so you get wrong coordinate values. See the link above for details.
By the way, be aware: most online maps (like Google, Bing, OSM etc.) use
EPSG:3857 for map display, but coordinates are shown in
EPSG:4326 to comply with common practice of using lat/lon values (e.g. GPS). This can be quite confusing.
Screenshot 1: with project CRS
EPSG:4326, the OSM basemap looks like this - warped (cf next image), but the coordinates show the correct lat/lon values:
*Screenshot 2: project CRS in
EPSG:3857, but showing coordinates in
EPSG:4326 (WGS84, lat/lon) by right-clicking on the map canvas. In the coordinates field at the bottom, it still shows the coordinates in project's CRS, here