For family, the only issue was confusion in Element for the Sign In vs Sign Up button. I had given them credentials myself to make it easier, but one of them tried using "Sign Up" with those credentials, which of course led to "username is taken" so they signed up with a different username.

I had started 1-on-1 conversations with all of the other family members, but since this one created a new account, they started a group conversation with me. So, they are listed under group conversations for me now, but meh, that works too.

I have a 1 GB node on Linode which is just a bit too little it seems, especially when joining the larger rooms on federated servers. However, I managed to make synapse work with systemd so now it just autorestarts if it ever crashes. I don't even notice anything anymore. Getting synapse to play nice with SELinux and systemd was by far the biggest challenge, but that's unrelated to federating.

Currently synapse is idling at 20% mem usage and barely any CPU usage.

Another non-federation-related issue is that I also had a minor issue where Nginx limited uploads to 10 MB which is a bit harsh for uploading videos. Took me a bit to figure that one out, but in the end it was just adding one line to /etc/nginx/conf.d/matrix.conf in the server sections, i.e.:

client_max_body_size 250M;

Setting up the rest was pretty straightforward. I even got a TURN server running as well even though I don't really use the video calling part yet.