I use Mullvad VPN, mobile and OS and there I can set a custom DNS server. Just added the IP of the pkdns server and voila, works like a charm.

Also works with Proton VPN. 

 Ah interesting... I wish Warp allowed that. Will try it. 

 Yes, but with my Qubes-OS system I have problems.

At some point I wrote manual configs, I have to straighten that out again so that all App-VMs can also resolve. 

 Happy that you are enthusiastic about this 🙏