Host both. Keep plex up for your gma, Jellyfin for everyone else. Tbh Jellyfin is also pretty intuitive. Currently I'm hosting both, but my gma doesn't use it, so I'll probably move completely to Jellyfin.

Why? It's been much easier for me

I understand. I have converted fully to JF which required people to get onn players, and tunnel into my network and it was a lot of work on my end too.

Do what works for you and them.

The people asking why confuse me...y'all acting like jellyfin is easy to use on an off-site tv when it's literally not for non tech savvy people. I don't understand why jellyfin just doesn't nut up and make an samsung tv client or something?

You can run them concurrently and let grandma continue to use plex.

if my parents can navigate it your grandma can :)

If your grandma can handle torrenting over VPN, then she can probably handle Jellyfin.

I've heard people had luck with Tailscale playing nicely with non Plex options. I can't say I've tried it. Though I do use Tailscale. Essentially if you setup Tailscale for Grandma it'll be like she's sitting on your local network. Even better, set it up on her router and you can literally debug all her Internet problems if you can ping it.

Beyond that a raspberry pi with a battery backup on a 4G subscription connected to the router. That would be the ultimate "grandma" setup. Connect her router/modem power to remote power cycle. But I digress.