The DuckDuckGo VPN is the only VPN compatible with DuckDuckGo App Tracking Protection for Android.
Why don’t other VPNs work with App Tracking Protection?
Android only allows one active VPN interface at a time per device, and while App Tracking Protection is not a VPN itself, it does require a VPN interface to function.
DuckDuckGo VPN can share that VPN interface with App Tracking Protection because both features are managed by the DuckDuckGo browser.
Learn More
Prior versions on GitHub.