Is there any softwares to download and sync with YouTube/PeerTube/Lbry?
Just so I could like sync a channel, for example, download the current available and upcoming videos so it could be accessed via Jellyfin (or something similar, or maybe upload them into a locally restricted hosted PeerTube) locally?
Grayjay has integration with Youtube, Peertube and others, so maybe that to download? Do mind one or other integrations may be spotty (e.g. Nico Nico through a 3rd party plugin) and or not supporting downloads (e.g. Spotify). And Youtube specifically requires login there for you to download videos marked as mature.
It's mainly an Android program. But if you'd still use it, Android has a desktop/x86 version if you'd be so inclined, and maybe (hopefully) the PC version is updated into a decent state now.
If you use yt-dlp, I think it's interesting to mention it allows attaching the video's description into the file's comment, like in the following command: yt-dlp --embed-metadata --parse-metadata "description:(?s)(?P<meta_comment>.+)" https://video-link/
It also has the option to download, as well as embed, different audio and subtitles languages, iirc, as well as fetching the auto-generated dubbing and subtitles from Youtube. Just can't remember the respective flags as I may use it only very sporadically.