I use some website daily that was signed by R11 certificate. But R11 certificate is not installed on my Android device. So I get the error "Connection is not secure":
""Your connection is not private
Attackers might be trying to steal your information from wpoatx.com (for example, passwords, messages, or credit cards). Learn more
NET::ERR_CERT_AUTHORITY_INVALID
This server could not prove that it is wpoatx.com; its security certificate is not trusted by your device's operating system. This may be caused by a misconfiguration or an attacker intercepting your connection.""
It will be very helpful if you can provide the certificate file of R11 Certificate file so that I can install it on my Android device manually. (Its an old Android 6 device.)
You probably already know, but for the sake of completeness: if you're still running such old Android systems, you might want to consider updating Android if possible due to lots of unfixed vulnerabilities in these older, end-of-life software versions.