This community is mostly for the https://mastodon.social/@dungeons community, but feel free to post about general D&D, questions, development stuff, etc.
I've seen some concerns about Lemmy as a platform, so if that worries you there is a Kbin alternative Magazine here: https://kbin.social/m/dungeons
https://organicmaps.app uses Open Street Map data, and I prefer its UI over OsmAnd
If you're feeling adventurous, you can also contribute to OSM mapping with something like https://streetcomplete.app :)