I have Raspberry Pi 4B set up as TV box and for my own media like Kodi or Jellyfin, barely handles 4K but works. And I like how I can sync files or remote control seamlessly because it’s standard Linux not Android.
For mainstream streaming I really discourage form even trying, it’s a mess. If you plan to run any type of DRM media you already are on the lost position and might as well buy cheap Android TV stick for ~30$, because there would be no freedom gain with RPi, just big annoyence.
TLDR:
Linux for own media.
Android for renting.
Raspberry Pi for Linux.
Cheap TV stick/box for Android.