Looked at both YT archive tools. tubearchivist is really solid - I'm just not sure how I feel about the video metadata is not being stored by default and only as embed in the mp4 video file.

tubearchivist - https://www.tubearchivist.com/
✅ Archival of individual videos, channels and playlists
✅ Good UI to browse videos, channels and playlists similar to YT
❌ Thumbails and metadata are not stored with the video (only embeded in the mp4 file, cryptic folder structure). 
✅ REST API
💡 Higher setup complexity and memory usage (elastic search, redis)

pinchflat - https://github.com/kieraneglin/pinchflat
❌ UI can manage downloads but UX for browsing and watching videos is not good
✅ Archives channels and playlists
❌ No adhoc archival of individual videos
✅ Download folder with videos has thumbs and metadata (human readable folder structure with mp4, thumb, info.json)
✅ Simple setup (only internal sqlite)