Technitium does this incredibly easily. I fiddled with pihole and unbound for so long to get them to coexist properly, and pihole alone before that. The pihole part was easy although unreliable on a raspberry pi due to the sd card. It was better once I added an ssd to the pi, but it didn't have recursive DNS. Adding unbound and getting them configured properly and coexisting properly wasn't an easy task. Technitium has all of this in one package and was trivial to set up one or more clustered nodes. You don't need anything to ensure they both work together, the clustering feature does this incredibly easily. One goes down? No prob, I see a discord alert from uptime kuma letting me know. When it comes back up cluster mgmt syncs everything and they load balance again.

My current setup has an uptime of 210 days, and likely would be longer if it weren't for a power outage.

It really is so simple, I'd suggest everyone try it out. You can always change it back if you don't like it. And, like the pihole, you can load curated block lists.