I've been doing the self-host Plex server thing since long before it was anything else (late aughts). I don't use it for anything else. While I'm all for switching to something else, my tolerance to level of effort is quite low so inertia has been the thing keeping me on Plex.

How quick & easy would it be to convert to something like jellyfin for self hosting?

Potential gotchas: in terms of tech stack I run the server on a Synology NAS so would need something that runs there. And 99% of my streaming is to Roku sticks, so there'd need to be an app there.