Agreed on Hetzner, although I have used customer support—to add another distro option. Sent them a web link, and they had it uploaded under my account by the next day.

Nothing serious. In GNOME my alternate chars and compose were set to the same key after the upgrade; just had to change one. There was an issue with "sloppy" window focus, but they fixed that upstream before the official release of 45. I upgraded during the beta.

Librera Reader for everything. I use it for both books on a phone and comics on a tablet—covers both great! Plus it is on F-Droid.

Yep, except with http here (python3 -m uploadserver).

There is also Rocket.chat, to complete the list, though it is supposed to be difficult to host.

I would recommend Matrix. My small instance is running Conduit, and it works great!