you need to go to setting>general and toggle advanced mode. then back to settings>dns protection> dns filtering>dns filters and add this url
it willactivate the DNSfilters to block in app ads
I use the Samsung note 8 with oreo. After disabling and enabling protection. It becomes stucked and the enabled icon is still greyed out. And disabling protection takes a long time unless the screen is put off and on again. Using the latest nightly!