How to keep IP when installing new firmware on router?

I need to replace a firmware on a router and usually when I do that and can’t keep all settings I need to set up tailscale from scratch and the device gets a fresh IP.

How can I “transfer” a tailscale IP?

On Ubuntu tailscale seems to save its state in /var/lib/tailscale.

Could try copying this folder between machines, and seeing if that is enough to migrate the IP and the rest of the machine configurtaion.

or is there a way to assgin a static ip for each taliscale node.
to hardcode the ip address.