Even if a game doesn’t look like it’ll work based on protondb, try it anyway. Many times I’ve had games that were marked as low ratings start up without any changes lol. I remember even when d4 beta came out, I saw people struggling to install and play it on the first weekend… Worked out of the box for me.
Try using the private IP options instead and see if that works. The generic one being 10.64.0.1, but other options that include ad voicing and such ranging from 100.64.0.1 to 100.64.0.25 or something like that. I’ve got my entire network setup behind their VPN and a a pihole pointing to one of their private DNS addresses without any issues. I left their pubic DNS years ago so that I could make sure my DNS requests were always within the tunnel instead