I switched from Plex to JF after being a plex user from the very beginning. It's not as polished as plex but it has none of the bloat and works flawlessly for me. It's super easy to manage my libraries and the meta scanners work 95% of the time, very rarely needing me to manually tweak data or images for media.

Jellyfin android works fine on firetv. The only thing you might struggle with if you run the server on a pi is transcoding, especially if you have 4k media files.