Does Dropbox use proper filesystems? I considered using Amazon's S3 to host a repo but apparently it may not work properly since it's not a 'proper' file system
They’re entirely separate things. Dropbox syncs a local directory on your computer. S3 is a remotely accessible object store.
So yes, you can put a git repo in Dropbox if you want. But that’s still an altogether different thing than “hosting” a git repo like you might do with GitHub or Gitlab.
I believe they meant they'll fuse-mount an S3 store to a local directory and store a git repo in that. And presumably Dropbox will refuse to sync it because it requires the synced directory to be on one of a few specific filesystems.
