Title.
There’s also a version on the Play Store, but you should definitely get the F-Droid version. It’s the one with the full features enabled.
It lets you fully block some apps’ access to the internet, including system apps. Depending on your phone manufacturer, like Xiaomi and Samsung, they can be extremely invasive and show ads on your stock apps.
I haven’t tried that DDG app tracker blocker, but if it acts as a “local VPN”, then it probably works the same.
It does act as a VPN and puts the VPN icon on the top right (android)