You can’t really replace YouTube’s massive library yourself, the best you can do is avoid it but that’s hard too. As for the frontend, there is
NewPipe/Tubular (Android, also supports Peertube, media.ccc.de, SoundCloud, Bandcamp)
Piped (web, very privacy-friendly)
Grayjay (Android and desktop, partially open source, support for many services including PeerTube and Odysee, $10 or guilt-tripping infinite free trial)
I can recommend TubeSync, it’s a self hosted service to schedule regular download of selected content from YouTube. You can integrate it easily with Plex
Instead of using YouTube, use PeerTube
You can’t really replace YouTube’s massive library yourself, the best you can do is avoid it but that’s hard too. As for the frontend, there is
I can recommend TubeSync, it’s a self hosted service to schedule regular download of selected content from YouTube. You can integrate it easily with Plex