Like a lot of people, I hate advertisements. In my quest to remove ads as much as possible, I've installed an ad blocker in my browser. To go further, I've installed Pi-Hole to block ads for all devices on my home network. I've even setup firewall rules to re-route all DNS traffic through Pi-Hole. This setup seemed to work pretty well until I noticed I was still seeing ads in an app on my Android phone.
I use AdAway on android (https://f-droid.org/packages/org.adaway) and ublock origin on firefox/chromium. They work well enough for me. There are also doh servers that block ads and you can manually set them.