You will need ssh access to your USG.
I suggest running sudo su
so you're the root user throughout
- Download tailscale and put the files in /config/. Find the latest stable or unstable version for your USG's processor.
curl https://pkgs.tailscale.com/stable/tailscale_1.36.1_mips64.tgz | tar xvz -C /tmp
mv /tmp/tailscale_1.36.1_mips64 /config/tailscale