Syncthing doesn’t allow sharing Like, between users? You can set up a shared folder with that user, although I know it’s not the same.

I’ve recently been made aware of Copyparty, which is a web GUI for serving files, with great access control, and the main dev reported people have been running it over a Syncthing-synced directory without any issues. Has an Android app too. I don’t have any need for sharing over HTTP right now, but if I did, that would be my go-to.