For IPVT streaming there is FredTV

Steam set to launch in big picture mode is nice if you can run it on whatever you're using. I'm also looking for more apps so I hope more people reply.

Stremio, Kodi, Grayjay, Fcast, ES-DE, OpengamepadUI, Plank, Aurora, Nymphcast, DuckStation, Retroarch

Theoretically, you should be able to install waydroid or something similar and android tv apps. I haven't seen it done, so I'm not sure if everything will play nicely. I'd be interested in reading a writeup from someone trying though.

Did you ever get your existing jellyfin server figured out?