Copyparty is easy, but if you can both set up syncthing, that makes it a breeze. I have a sibling that lives across the Pacific and last time they visited I set up syncthing on their laptop and when either of us wants to share something, we just drop it in that folder and wait a minute or two.

Dude just could have said something like,“Hey, I’m a developer of Plex and have really enjoyed my experience using it. Let me know if you’d like to see something added/fixed.”