a TorrentFreak article got me spooked so I fired up the ol’ yt-dlp. Got the entire channel, including comments, description metadata, and thumbnail images.
A significant number of videos were actually unavailable because of an odd YouTube bug where 15+ year old videos were listed as “currently being processed”. I may re-run this later (since I ran it in archive file mode) to get the missing videos, as it seems there may be about 300 out of 4911 videos missing.

yt-dlp does support fetching comments and description text - if you use the
--write-info-jsonand--write-commentsoptions, it will save them as a JSON file alongside other video metadata.