I don’t know of any single full documentation, but one immensely useful link someone posted is to https://browse.feddit.de/
There you can much more easily search for communities than the native search seems to allow.
EDIT - just found documentation: https://join-lemmy.org/docs/en/users/02-media.html
I’ve not looked through it yet, so can’t comment on how good it is, but might be useful.
Yep, OP’s link works for me, using Sync, with the link itself opening in the YT app.