I am the original poster of this thread. I am speaking only for myself, but it now works as it is supposed to for me. I have a consumer outlook.com e-mail address using an Outlook 365 consumer subscription. After a clean install of Windows 10 and Office365,
I can simply add my outlook.com address as an account. I then receive mail for both the primary account and the alias. I can also choose to send from the alias when creating a new message, and the alias account is used as the source of replies to those messages
to which it is sent. It only took seven or eight YEARS, but it seems to be working now.
[Edited for more info] For what it is worth, I am based in the USA. I don't know if that matters or not.
Of course, Clutter and/or Focused inbox are inconsistent steaming piles of crap right now, so there is that.