My pihole isn't running on a "client" machine, though it is running on a VM on the home router/server just to keep it entirely separate to aid maintenance. A container would do the job too. I was just pointing out that the OP wouldn't need new hardware to set up pihole.

And in my case the VPN is not just for accessing my ad-/malware- blocking DNS resolver, but also for accessing other local resources and for general paranoia (nothing goes over the mobile network or public/guest WiFi unencrypted). Useful extra feature: because payment processors think I'm at home I'm bothered less by extra identity verification steps than I would be if my source address and therefore derived location changed regularly.

DNS traffic going through the VPN stops the network intercepting and forcing it through their resolver anyway (I'm looking at you, Sky) and means that I don't have to make my DNS resolver visible to the unwashed masses.

So I'm not just being obtuse. IMO, anyway.