Blokada - Open source advert/tracker blocker
There are a few good blockers for non-ROOTed Android devices, but since version 3, Blokada has a useful extra function usually reserved for ROOTed devices.
Since v3 it will now let you set alternative Domain Name Servers.
Blokada is overflowing with blocking options, which at first glance are somewhat overwhelming, but once you poke around you can see they are broken down into sections with clear info describing their use.
It also has sensible groupings for different RAM footprints, which is very useful for low RAM devices.
Like all the best blockers it is banned from Google play store as it will block Google trackers and adverts, so the release in the play store will only change your DNS.
Standalone DNS changer