Folks at Coder authored a p2p file transfer tool using Tailscale (no account needed, the setup is entirely ephemeral, and the code apparently runs a Headscale control server in-memory): https://github.com/coder/wush

Unsure how Tailscale rate limits, if at all, such traffic flowing through its public relays ("DERP"), as a tool like this is just ripe for abuse?