Do you know [QuickMapsServices plugin][1] fort QGIS? This plugin provide more than 500 base maps (OpenStreetMap too). 

The [QMS][2] service also integrated with [NextGIS Mobile][3] (a QField alternative). See documentation about how to add base map: http://docs.nextgis.com/docs_ngmobile/source/load_geodata.html#creating-raster-layer-from-external-geoservice

[![enter image description here][4]][4]


  [1]: https://plugins.qgis.org/plugins/quick_map_services/
  [2]: https://qms.nextgis.com/
  [3]: http://nextgis.com/nextgis-mobile/
  [4]: https://i.sstatic.net/HiwdO.png