This is less true of software like the one mentioned in the article that are intended to be self-hosted, though: I have to walk my users through using it anyway

This is less true of software like the one mentioned in the article that are intended to be self-hosted, though: I have to walk my users through using it anyways and so I can show them FileZilla or install a SFTP filesystem on their computer or setup syncthing/dropbox for them to handle uploads. There’s lots of ways to avoid exposing a custom file upload service for this sort of thing.