If you want the instances to sync, you just need to sync the directory. (I currently use nextcloud sync for this, but in the past I used synching and before that btsync)

If they dont try to modify the files at the same time (with sync delay) there won’t be any issues. If they do grow out of sync, you can fix pretty easily with db repair.

Something like that is probably technically possible, but you’d need to do a bunch of work.

Plex Plugins can’t provide media sources anymore, so you need to do the trick plex_debrid is doing where you add stub sources to the plex server library and serve the files from a virtual filesystem.

You might be able to re-use the plex_debrid code but use youtube-dl instead of rclone

This uses ffmpeg under the hood and muxes the file into a .m4a file without transcoding. Basically keeping whatever compression youtube used for the audio (which is some sort of mpeg4 compatible audio, probably depends a little bit)

This still recompressed, but it’s the best you can do using youtube as the source.

• uploader (almost certainly, but theoretically you could skip this step if you encoded your video well) compresses audio
• uploader uploads to youtube
• youtube re-compresses the audio again (almost certainly transcoding into a different codec)

I mean people said this about SponsorBlock, but it turns out you can crowd source the timestamps… If you built an easy enough UI.