Wireguard setup fail over connection

[thisisme]

Hi

I'm routing part of my traffic via proton VPN with policy routing. I used this tutorial https://docs.opnsense.org/manual/how-tos/wireguard-client-proton.html

Now.I want to setup a fail over connection to another ProtonVPN server. Unfortunately this does not seem to be possible with Wireguard. So I'm using a OpenVPN connection for the second tunnel.

Unfortunately I ran into another issue: The tutorial suggested to add the ProtonVPN server as the upstream DNS-Server. This server is only reachable via the Wireguard Tunnel, but not via the OpenVPN connection.(Different IP Segment).
I tried to remove the upstream DNS config and set the outgoing interface for unbound to my Wireguard tunnel, but with this setup unbound can't resolve anything. It looks like unbound can't properly route via the Wireguard interface if it tries to reach a public IP.

What did I wrong?