I would recommend you look at some other guides before you do this but the gist is My Account > Your Account > Manage Account Information. Then you can add a new email that you do not share as your primary login email, and disable login from the email you use to send emails.
However, I can use any of them to initiate a login attempt. I have my account set to passwordless, I don't know if that is relevant (every login attempt triggers an MFA prompt).
If I click on "Edit account info" I am taken to a page where I can choose which address in the "Primary", but given that ANY of the aliases can be used to intiate a sign-in, I don't see any benefit in changing that.
EDIT: I wasn't being adventurous enough. The option to change which aliases can be used to sign in is under (surprisingly) "Sign-in preferences".
In my defence, that page wasn't loading properly in Firefox with all my privacy add-ons enabled. I was able to access it in Edge.
EDIT2: I've changed my primary alias to a newly created one. If I am still able to sign in OK in a couple of days, I will disable the old primary for sign-in. I hope I don't live to regret this!
Would show any logins or security info updates etc
So there is no way to flag them as malicious and if you accidentally accept, then it’s already too late.
Pretty annoying setup.