A few things I would check, assuming that you’ve used --advertise-routes=192.168.1.0/24 on your RPi
1: have you set your subnet routes on the admin console?
2: If your remote machine is linux, have you used --accept-routes when launching tailscale?
3: Can you ping the printer using 192.168.1.123?
Are you trying to run the printer discovery and reach to printer, that should not be expected to be working as it uses multicast. Use the subnet IP to reach your printer and it should work.
Thank [darshinimashar]
For those people who came later. I have an Epson printer, and it does not appear on the list automatically.
But when I switch to manual IP and type my local IP printer, It works perfectly (Just ignore “Communication error” from Epson App)