Der Habeck hat wohl zu viel vom eigenen Cool-Aid gesoffen?
poVoq
XMPP clients for Android are great, for iOS a bit less so. On Windows / Linux Gajim is probably the best option right now. JoinJabber.org has a good list of up to date clients (do not use Pidgin, it's horrible and super outdated).
In general the main downside compared to Discord is the lack of voice-channels. 1:1 voice or video calls work great with the Android clients and group calls are partially supported in some desktop clients (that is currently very active field of development for XMPP clients).
So zu sagen: "Make Europe Great Again"?
wer Sarkasmus finded kann ihn behalten
Why wouldn't XMPP work? It fulfills all your requirements and has nice modern apps, especially for mobile. Definitely better than Matrix.
The easiest to get started with it would be setting up a Snikket server (Prosody based, but pre-configured for small private groups).
Mostly bug fixes.
What makes you think so? It seems rather openly "leftist" at least for US standards.
Feddit.org is only majority German speaking (it's actually run by an Austrian foundation) because people from feddit.de needed a new home. It is not per se only for German communities, for example /c/europe@feddit.org is in English.
Since they run their site through Clownflare, it looks like they are hosted in the US, but their server is actually in Finland (at least as far as I know, might have changed recently).
I think one reason has to do with digital sovereignty. Especially people in Europe are not happy with the dominance of US based social media sites and thus are more likely to invest time and effort into local alternatives. They are also more likely to be concerned about the near total lack of legal privacy protections in the US.
Small correction: slrpnk.net is hosted in Portugal and not Germany, but we do have a German speaking admin and our founder is Italian.
Your best bet is probably to ask on the official channel.
But maybe @nicocool84@sh.itjust.works is willing to give some hints here.