I’m not sure what you mean by IPV6. I don’t use it. All devices in the house (except the servers) use the Pi-hole address for DNS. For iPad/iPhone you have to set the DNS manually from the WiFi tab of your settings. Tap the little blue i with a circle around it and then tap on the Configure DNS. Don’t use a second DNS address thinking you will need it when you leave the house. Each WiFi you join will have its own DNS server supplied from the network’s router.
OMV 5 (current) - NanoPi M4: Nextcloud, Plex, & Heimdall - Acer Aspire T180: backup - Odroid XU4: Pi-Hole (DietPi) - Odroid HC2, Raspberry Pi 3B+, and HP dx2400: testing.