A raspberry pi running Kodi has been serving me well for years.
Easy install paths include LibreELEC and osmc. I believe both are based on debian.
FWIW I chose and have been happy with osmc.
Regardless of the choice, Kodi has a plugin system for things like YouTube, you can access your media via the jellyfin plugin/app, or by pointing Kodi at your media. It has a remote app available on android and iOS, and for the most part just works.
Pi4 8gb. FWIW, the 5 is not great for media. I don’t remember the details, but iirc they removed hardware decoding from the 5.