Mullvad offers such a service for free. https://mullvad.net/en/help/dns-over-https-and-dns-over-tls

But you can't set them as system DNS (UDP/53) AFAIK

https://www.joindns4.eu/for-public has an endpoint that includes blocking ads.

You can use https://dnsforge.de/ (Sorry, page is in German)

I've been using nextdns.io (which seem to have founded this initiative) for a few years and it works pretty well for that

Try it with a pihole

If you use a 'pihole' or similar setup, change the default away from "127.0.0.1" to "NXDOMAIN".

not answering certain DNS queries would be something! lol

That's what DNS filtering is for: https://www.cloudflare.com/learning/access-management/what-i....