Could you run a user space s3 filesystem that jellyfin thinks is a regular disk filesystem.

You can, it’s just suboptimal in my experience and incurs troubleshooting time. I’ve been meaning to put a bounty on S3 compatible support via a fork (maintainers are not interested and believe posix file system is preferable), just haven’t had the time. Hopefully soon!

Desired pipeline is “Ingest->MusicBrainz->Object Storage (music bucket, write once read many)->Serve to various clients from middleware server (Jellyfin).”