Tailscale plugin latest release are support to use a other peer to exit-node. The release note say that not enought to enable it, it need some firewall / NAT settings. I try to configure it, but not Work... my goal to my full subnet use mullvad exit-node to access the internet.
My exit-node a mullvad Endpoint . (I bought the Tailscale mullvad plugin)
So far that i set it up:
Create a new Gateway (set the opnsense tailscale IP address)
(https://i.ibb.co/JR65kKcN/image.png)
Add these rule to LAN
(https://i.ibb.co/9kzRT2G4/image.png)
Add these rule to Tailscale0
(https://i.ibb.co/p6zqLzR3/image.png)
Add hybrid NAT: Outbound
(https://i.ibb.co/JMpbh7v/image.png)
It's been a while since I set this up and tested it but I think the gateway IP should be the remote exit node's Tailnet IP, not the OPNsense Tailnet IP.
Also try it, but not working... Seems it will be work a "normal" Exit-node, but not the Mullvad...