Best move is to try to do pivpn installer again and when it says we found a pihole installation do you want to use pihole with pivpn say no. If it still breaks uninstall pihole, install pivpn l, then reinstall pihole

I’ve never had an issue with pihole (i run them on the same device). Pivpn ibstaller typically detects pihole and juat sets it up as pivpn dns but you could also have it not do this in the installer

The easiest way is with pivpn

https://www.pivpn.io/

https://github.com/rogerfar/rdt-client

This masquerades as qbittorentt allows you to use RD with *arr