Automatic Client Certificate selection with Android

I am building an Android App and my backend wants a certificate to be installed, so it can be accessed.
I also have a (different) Web-App and there the certificate is installed in the browser and the browser asks, when connecting for the first time.
So what I did is, I installed this certificate on the Android device and used “App and VPN” option. When I now use the Ionic App as Web-App and open the page in Chrome, I am asked to select the certificate and then it works.
If I now deploy an Android-Ionic-App and open it, it says “No certificate selected”. So the question is, how can I get the App to select the certificate? Can this work automatically?
I found this old thread here, but it seems the plugins don´t work anymore:

Any ideas? Thanks!