A good way to work around this is to have a small server in your house as the first hop for ad blocking, and use the second hop (set the DNS servers of your DNS blocker) as your ISP.

If you use a Unifi router you can use it for this purpose (and caching) by broadcasting its IP as the default DNS server using Network options. It caches/forwards/filters any requests according to how you setup DNS in Firewall settings.

Networking isn’t my strong point, but my impression is that if you do this (e.g. with a Pi-hole) there isn’t a way to gracefully failover all your in-home devices to the second hop when your Pi-hole is down. In practice this means that to avoid introducing an extra point of failure you can only really do this with an appropriate router, which pigeonholes your router selection if your preferred router isn’t one that already supported this.