VLC will let you do this! This is how I got all of my music off of my Linux machine over to my iPad and iPhone. I haven’t tried transferring from iPhone back to Linux, however.

Had this exact thing happen to me. I was hosting vaultwarden on a raspberry pi and then it fell over. My client devices had caged versions of my vault, but I couldn’t make changes to it. I quickly moved over to Bitwarden and it’s been fantastic.