CA certificate somehow not taken by browsers on android
Firefox on Android
You don't have to add your custom root CA certificate to Android to let Firefox trust it. Similar to the Desktop Firefox versions Firefox maintain an own root CA certificate store you can add certificates to.
The only difference to the desktop version is that there is not management UI for adding certificates.
Instead you simply have to download a root CA certificate (DER format not PEM format) using Firefox Mobile then a dialog appears where you can mark the certificate as trusted for identifying web sites and/or mark the certificate as trusted for identifying e-mail users (pretty useless on Firefox on Android but it can be selected).