You have no reason now to be not using Mullvad's DNS service.

"Our Encrypted DNS servers have now been converted to run from RAM!

This is completely cost-free, and available to anyone that wishes to have a trustworthy, audited Encrypted DNS service with optional content blocking!"

If you use Android just set you Private DNS under settings to : base.dns.mullvad.net and never see a single add across apps without any privacy concerns.