sudo tailscale up --advertise-routes=10.0.0.0/24,10.0.1.0/24
Then you can get to anything via it's internal IP address. I have a bluetooth router on my network that I don't want to install Tailscale on. It's on a permanent address of 192.168.1.13
I do this on the router inside my office subnet:
sudo tailscale up --advertise-routes=192.168.1.0/24
I do this on my home debian machine (lets say it's on 10.1.1.13):
sudo tailscale up --accept-routes
From my home network I can now open the web management page on 192.168.1.13. You can go further with DNS stuff but you don't have to.
[1] https://tailscale.com/kb/1019/subnets/