Update: After discussion with Massimiliano Ziccardi I've followed the docs for working with self-signed cert. Results:

iOS

• App metrics - worked fine
• security metrics results do not appear in grafana

Android

• installed the certificate to device/simulator, however publishing of app & device metrics still does not work
• error: [AeroGear] Error publishing device metrics: java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.