As for cross platform, there are Element and FluffyChat. There is also nheko I can recommend for desktop and cinny on web. Here is a comparison between different clients fyi.If you don't insist on matrix, Snikket might be a good option too.
I can't wrap my head around the idea of letting some other country's military have bases in your country.
It's something close: https://discourse.mozilla.org/t/about-config-missing/66537/6About:config is not a feature that most people will use and it can make your browser seriously unstable.
Fennec also has about:config support. It's a firefox feature that's removed "because it's dangerous for users" 🙄
Yep. Lemmy feed for example is algorithmic