A lot of people did jump to Mastodon, and apparently it had had another large influx of users yesterday after all the Twitter shenanigans. Not everyone stays though, obviously.
I think part of the issue some have with Mastodon is the lack of Twitter's algorithm. It's absolutely true to say it's harder to find people and topics to follow on Mastodon for the simple reason that you're not getting anything shoved in your face, which is a massive plus point for many (myself included) but can also make it appear initially less appealing.
You probably know this already, but X11 hasn't been dropped completely. You can still install what you need from the distros, and then the X11 option will be present and correct in SDDM.
sudo dnf install kwin-x11 plasma-workspace-x11