This is much simpler in OPNSense

Add gateway

System -> Gateways -> All

Add Gateway

Change Interface to WAN.

Add your primary OVH IP gateway in the “Gateway” field (this will almost certainly not be the gateway for your IP address block) and tick the “far gateway” box.

Hit save and then reload

Adding more IPs

Go to the firewall -> virtual IPs

Add an IP Alias, add the IPs one at a time with a /32

Your IPs are now ready to use!

LAN Internet

Firewall -> NAT -> Outbound

Manual Outbound NAT rule generation. If it isn’t created automatically add a rule with the Interface of WAN, source of your internal IP (192.168.1.x/24) & any VPN IP leave everything else as default and save. Check that your WAN address is chosen rather than interface address (or your outgoing traffic will come from any of your external IPs)