I also have a Pi with HomeAssistant that I’d like to migrate

I would (read: does) keep it that way. When your server inevitably goes belly up because of a misconfigured firewall or whatever you’ll thank yourself when the lights still turn on and your robot vacuum keeps going. No stress to fix things. And when your SD card eventually dies you just pop in the backup card you have lying around.

I am wanting to do this in the most efficient and economical way but I’m not sure what the best path to choose is.

What’s wrong with keeping your old hardware? Spend some money on a silent quality case, a few quiet fans, a suitable power supply and some disks. The rest can be bought used if you need it, dirt cheap. Find a somewhat new Supermicro motherboard with a mounted CPU on eBay for a few bucks and be done with it. It doesn’t sound like you need a monster machine. Some overhead is always nice, sure, but you can always upgrade in the future.

Migrating data is a PITA no matter what so can’t help you there.

As for the OS. “Not Windows” is probably a bit intimidating at first but you seem to be pretty technical so it isn’t really an issue as long as you can read and process information. Do some reading on Debian or FreeBSD (or both). BSD isn’t Linux but if you’re not familiar with either one it doesn’t really matter. Just a matter of taste. Try them in VirtualBox and see for yourself how you feel.

And let us know when you buy your first rack. It’s just a matter of time.

Beats Kodi.

I see. The multi user support in Jellyfin is arguably one of its strengths so that’s a shame. Don’t have a good recommendation in that case.

Adult or not, Android/Google tv lacks good media centers or video players. Jellyfin, Kodi, Nova or VLC are basically your options and they are all crap in their own way. If you don’t want to watch something on Netflix, HBO etc. It’s really a bummer.

Are you hellbent on using Jellyfin? It’s basically a Kodi for dummies where they removed the best parts, kept the worst and and slapped on a pretty ui. It’s bloated behind the scenes and does have it quirks.

An alternative could be to just set up an NFS share with your media and use whatever player you like. Nova video player on Google/Android TV isn’t as pretty as Jellyfin but it gets the work done.

I’ve had zero issues with Infuse on apple tv. Easy to navigate, looks good and plays stuff on my network shares. I think there is support for adding a Jellyfin library as a source as well but I haven’t tried it.