You can install the client anywhere (including the Apple TV), but you need additional clients that can act as exit nodes. In my case I have also set up a Raspberry Pi as an exit node, and I can then load Tailscale on my Apple TV and tell it to use the Raspberry Pi as the exit node.
It works (now 2 weeks…) until you reboot the AppleTV. Then it’s over and you have to subscribe.
I add proton, surfshark and windscribe WireGuard config files but I could not connect after 3 days.
Interesting, it’s working for me with no payment restriction after a week, connecting only to my own WireGuard server (on a UniFi UDM Pro)…
Thats great feedback. I am intending to do the same