Why is necessary certificate when i use custom domain URL for discovery server?

Name, IP address, and authentication all come together to establish the trust to provide the certificate. Plex.tv is guaranteeing that this IP address & host is who it claims it is. That’s the purpose of a certificate, isn’t it?

Would you let just anyone have trusted, secure, access to your communication which will contain personally identifiable information (username & password)?

This might be of help in understanding.

Sure.

But why we limit in the fact that the determined ip address (which will out to be inaccessible) cannot be indicated differently for the creation of the certificate?
after all, I would just like to indicate using DNS the correct IP, providing the address on which the actual server responds, which will already be authenticated. and Plex.tv can check now the server to generate the new certificate on the new IP

Also let’s encrypt doesnt use IP address.

I’m sorry.

You are not understanding what I’m trying to say – and – I’m probably not breaking it down enough for which I apologize.

You cannot point your arbitrary things and try to use Plex’s certificate as authentication for HTTPS

If you have a pure IP-based DNS-lookup , without your own certificated domain, then it would work

HOWEVER

You have a certificate.

It ends right there.

I’m sorry but I have no further time.
You cannot interject your certificate into Plex without informing Plex (in the PMS network configuration).