Honestly, this is an easy way to share files with non-technical people in the outside world, too. Just open up a port for that very specific purpose, send the link to your friend, watch the one file get downloaded, and then close the port and turn off the http server.

It’s technically not very secure, so it’s a bad idea to leave that unattended, but you can always encrypt a zip file to send it and let that file level encryption kinda make up for lack of network level encryption. And as a one-off thing, you should close up your firewall/port forwarding when you’re done.

Yeah, if OP has command line access through rsync then the server is already configured to allow remote access over NFS or SMB or SSH or FTP or whatever. Setting up a mounted folder through whatever file browser (including the default Windows Explorer in Windows or Finder in MacOS) over the same protocol should be trivial, and not require any additional server side configuration.

Yeah, I mean I do still use rsync for the stuff that would take a long time, but for one-off file movement I just use a mounted network drive in the normal file browser, including on Windows and MacOS machines.