All my Thunderbird email accounts now show a red triangle.

Disable your antivirus mail scanning function until they can issue a trusted certificate, or follow the instructions they provided to trust their self signed certificates, but the IP address in your message is the localhost, not a mail server and the port is one usually used for proxies that can not communicate using regular mail ports because they are blocked. So I think you have a lot more to tell about what you are doing.

I do happen to know that the proton mail bridge software uses localhost and that port. Could this be a proton mail issue?