Not sure if this helps or is allowed but I figured out a way to get the tailscale package upgraded without needing a firmware upgrade. Steps are a bit involved but worked on my GL-AX1800 (Flint). My device is arm based but the tailscale arm package was just too big to put on the GL-AX1800. After a bit of testing I figured out I could use upx to compress the tailscale and tailscaled packages from the arm downloads (https://pkgs.tailscale.com/stable/#static) and move them over to the router. Once I replaced the files I was able to start the tailscale service from the GUI. Tailscale machine pages shows my system updated now as well.