I also got the AOL-Yahoo Oct 20 notice...
I am seeing the same error here for my AOL IMAP accounts, MailNews latest, and Vista32. I tried to remove and re-add the account or just manually switch from Normal password to Oauth2.
And MacOS and latest Tbird are working with AOL Oauth2, just as a test to make sure my account is functioning properly on the AOL side.
@roytam1Thanks so much for New Moon and MailNews!!!