I got it working pretty easily on Starlink with Tailscale. Didn’t even need port forwarding. The key was running the ARC app’s initial setup while connected to my local network. Then I could turn wifi off on my phone, connect to Tailscale, and ARC worked. How well it works will depend on what kind of mood Starlink’s in. When I first tried it this afternoon, it worked really well. When I tested it a little just now, there were a decent number of pauses while playing a test track. So YMMV but it’s definitely possible.
I’m not 100% sure, but I suspect what allows it to work in my setup is that I’m running Tailscale on a Raspberry Pi 4 configured to route my local subnet over Tailscale. So any device that connects to my Tailscale can access any device on my local network even if it’s not running Tailscale itself. My theory is that ARC is actually seeing my core as being on the local network, and that’s allowing it to work even though the ARC settings in the main Roon app says “not ready.”