4.3. Basemap tiles services
NextGIS Geoservices allows you to add vector and raster maps with GL styles:
Klokantech 3D
Klokantech Basic
Bright (nextgis)
OSM Bright (osm-bright)

Pic. 4.2. Basemaps NextGIS Geoservices
Note
A personal API key is required to add data (by default apikey is in the query string, blurry in the image).