For gaming you can just use steam. You can see which game works and the corresponding distributions/configurations on ProtonDB; Helldivers 2 get’s a GOLD status (https://www.protondb.com/app/553850).

Yep, Germany in general has a pretty active open source community, so there are already a lot of alternatives out there. Unfortunately, most IT people are bad at marketing, which is why hardly anyone knows about these alternatives.

Their official server in the fediverse (https://social.bund.de/public/local) with currently 99 active government agencies and institutions.