Hi,
you can use any Leaflet compatible layer you like, see Frontend customization - Gramps Web
For instance, Gramps Web by default uses Carto Voyager (see gramps-web/src/components/GrampsjsMap.js at main · gramps-project/gramps-web · GitHub), while Grampshub uses HighRes tiles from MapTiler (which requires an API code, which is why we don’t set it as default).
Gramps Web v24.7 also introduced OpenHistoricalMap as a new layer, which uses vector tiles (high res!) and displays time-dependent place names in the local language:
FYI: the frontend language settings and serverLang don’t have any impact on map language.