It's not super easy, but you can install it on tizen tvs by enabling developer mode. I was able to follow this walk-through to get it on a new TV for my relatives.
https://github.com/Georift/install-jellyfin-tizen
Since their TV was newer, I had to do extra steps to create a custom certificate.
The whole process took a while, but it's doable.
I've only personally used the tizen app a couple times, but my relatives have used it a bunch with no reported issues. I have not had to update it yet, but it's only been a few months. Definitely not frequent updates. My jellyfin server has had one update since then, but even the server updates aren't coming in on a weekly basis, so I don't expect their client will break anytime soon.