Sempa
I only had bad luck with German speaking privacy communities. If you find a good one let me know. I could give an anti-recommendation of a popular German privacy forum. Most of them had absolutely no clue about security with very outdated views (like a decade or more old) and a lot of FUD, especially about Windows and mobile OSes. I gave up, because I did not want to argue with multiple people attacking me because I had a different view on security.
Would recommend to use the GrapheneOS communication channels and especially listen to the advice of Daniel Micay and other project members. PrivSec.dev and Spite are also good on Matrix. Also following security researchers on Twitter and Mastodon can help. These are only in English, but I guess that's still better than falling for misinformation.