A single global IPv4 address, as assigned by your ISP, would identify your router. While it is true that the corresponding complete IPv6 address is somehow derived by your IPv4 address when IPv6rd is in effect, exact mapping procedures would depend on your ISP - but again identifying only your router.
All other devices in your network are assigned a private IPv4 address (commonly by your router) and may construct an IPv6 address by combining your IPv6 prefix (as provided by your ISP) with an interface identifier (as calculated by the device itself).
If your router does not support ULA prefix assignment, you could try and use your Pi-hole machine’s non-routable(!) link-local IPv6 address (from
Note that devices need to be within the same network segment for this to work, i.e. commonly all devices need to connect directly through your router - any L3 switching will prevent devices connected through such a switch/router/AP to see and communicate with Pi-hole’s link-local address.