It’s open source and gives you a lot of fantastic features that are locked behind paywalls and more on plex. But I will be honest it’s not nearly as simple and setting it up so I could use it outside of my home network took a week of figuring out issues with proxies.

You can keep using plex but if you have a good tech understanding jellyfin is pretty nice.

For your computer troubles I would say you can skip the pi completely if you have the space and get something like a cheap optiplex. They are dirt cheap used and can give more oomph and customization for hardware later on and are really simple to get any Linux distro on.