It should be noted that setting Adguard as your DNS will allow Adguard to track the domains you visit. The latest info I can find is that a lot of their team is still located in Russia, which makes them susceptible to government demands regardless of their intentions.

DNS adblocking should be the last resort. On Android there are many ways to do system wide local adblocking (with and without root). Don’t know about iOS. Alternatively you can do network level blocking with something like a pi-hole.