This comparison looks neutral: https://www.freie-messenger.de/en/systemvergleich/xmpp-matrix/

I always run occ upgrade and occ db:add-missing-indices after a package upgrade, just to be sure that I do not miss any database migrations. Using Archlinux I wrote a pacman hook so that it happens automatically.

You could have a look at Kerberos. That’s what Microsoft took as base for AD afaik.

I use the Nextcloud news app which is a RSS feed reader. But mainly because I run a Nextcloud instance anyways. For news only I would not install Nextcloud - too much overhead.

I had no problem to install my CA on my Pixel (Android 13). I read that this was not possible for some time but Google changed it.