Unbound DNS through VPN

[FredFresh]

I am trying to forward all the traffics outcoming from WAN interface to a gateway group (that has inside 3 wireguards VPN and, as last priority, the WAN interface itself).

The three wireguard are used only for outgoing traffic (provider is Proton) and are properly working.
I just miss the last step to forward what is processed directly by the firewall and go outside through the WAN, like the unbound dns external request.

I am using an external DNS provider  with Unbound DNS (not the one provided by the VPN provider).

I am already trying since several weeks and read multiple forums/posts but no real solution was defined.

I read several times the opnsense guide about the the DNS leak, but I do not understand what they suggest in a case like mine.

https://docs.opnsense.org/manual/how-tos/wireguard-selective-routing.html  I think the poitns 3 or 4 of the DNS leak paragraph.

Anyone was able to achive this?

[FredFresh]

Additional info: i also tried to select the outoing interface (within unbound dns settings) but it has no effect. I also restarted the firewall, but no effect