I can see some things being block via the query log in the pi hole interface, mainly analytics ad telemetry but still getting ads on the home screen and in the browser.
I have several IoT devices that are hardcoded with public DNS. In my case, I've created a couple of firewall rules on my router to enforce DNS. For example
Rule 1 - allow your LAN devices access service type (DNS) to your Pihole
Rule 2 - allow your Pihole service type (DNS) outbound to the Internet
Rule 3 - deny your LAN devices service type (DNS) outbound to the Internet