To be able to filter HTTPS traffic (which is extremely important as most ads use HTTPS), AdGuard needs to install a certificate into your device's user storage. On older versions of Android OS this was done automatically, but on Android 11 and later users have to install it manually.
If you experience issues during the manual certificate installation (for example, you installed the certificate, but the application keeps ignoring it), you can find possible solutions below.
If you use the Secure folder on your Android (this applies mainly to Samsung devices), you may face some difficulties when installing the HTTPS certificate. The thing is that the Secure folder has its own storage where the certificates are stored. However, in case you do everything according to the instructions described here, the certificate is installed into the main storage and plays no role for your ad blocker in the Secure folder. So, in order to resolve this issue and install the certificate for your AdGuard for Android into the Secure folder's storage, follow this instruction: