I have read the instructions of February 2020 for changing an email address. When I go to edit the profile, there is no entry for an email address nor a “change email” button.
In the meantime, my email address is gone and I can read posts by logging in, but I cannot receive any messages at the old address.
I also cannot log in as a developer because the site sends a confirmation email to my old address, which I cannot read.
The issue is that you do not have access to your old email address. Without this, it is impossible to verify ownership of a developer account. Folks must be able to prove ownership, or else it would be too easy for someone to steal other peoples accounts.