There is already one. I remember using it. But I think the linux one works better than the windows because of better integration.

Hmm. I did not know that. Why?

Instead of using Gmaps. You can try

1. Organic Maps (Simple and clean app that just works)
2. OsmAnd (Full of great features but it may be too much for you). Supports realtime map update in pro version or the fdroid version.
3. Magic Earth but i think it is not foss
4. Mapy.cz uses Openstreetmap but it also does not seem to be foss. But the map is updated in real time.

PixelDroid is the main app for Pixelfed. It is not the official app, that is still in development.

You can also login to pixelfed from https://tusky.app