I personally have my own DNS blocklist and only use that. But according to a reply from @Support they use some well known blocklists and their custom list to compile the domain block list:
If you are facing issues only with Ad Blocking DNS, I would recommend you open a support ticket and discuss it with them. Make sure to mention the apps/services/websites that are not working. And in the meantime, just use a different DNS. In case you want to block ads, try using AdGuard's DNS:
Default (blocks ads, tracking domains) :
94.140.14.14
94.140.15.15
Family Protection (blocks Def