Instructions (Android)

  1. Download the certificate from https://letsencrypt.org/certs/isrgrootx1.pem or transfer it to the device.

  2. Open the downloaded file. It should open a dialog that let’s you import the certificate. In case this does not work, you can start the import from the system setting point “Security settings” > “Install from device storage”.

    In the resulting dialog specify any name and to use it for “VPN and apps”.

    Android CA import

  3. Now you can select the new certificate on the VPN setup screen:

    Android CA select

And continue with the VPN setup.