I have an Yahoo! account associated with an outlook.com email address and I want to change it to my new iCloud email address without having to close the old account and register a new one. I don't even have an Yahoo! email address associated to this account. Is that even possible? I can't seem to find an option to change my email address anywhere on Yahoo!.
There's no way to do that now, you have to create a brand new account according to Yahoo!'s own website: https://help.yahoo.com/kb/account/create-yahoo-email-address-sln2059.html