Probably just an extension to existing ETSI legal interception interfaces[1] that I believe are required to be implemented by all service providers of a certain size in the EU. Your personal email server and private IRC network are probably out of scope.

[1] e.g. for email: https://www.etsi.org/deliver/etsi_ts/102200_102299/10223202/... - the specs are really boring to read and there are lots and lots of them, if you want to deep dive. From what I can tell it's basically just the service provider implementing an API client that feeds everything they're required to a centralized endpoint.

Network equipment of our ISPs already have this type of surveillance software. And there are number of examples where we have seen that it is being used by the government intel with success, and regardless of the communication chain being encrypted or not.

There's no shortage of ways. For example mandate preinstalling a spyware on every mobile device sold

Government controlled firmware on all devices that reads the messages after they are unencrypted?