Holy cow: That worked.
How in the world anyone would be able to determine this method without help like yours, is beyond me.
I do use 2FA as a matter of routine for various online accounts, including my Microsoft Account. But during this entire process, there was never Word One from Microsoft, or BB Hub, about 2FA being relevant to the creation of an account in the Hub.
I'm also a bit puzzled by the instructions at the Microsoft Using App Passwords page, the link to which you posted in the message above. The page said:
After you turn on two-step verification, you may run into issues if you use apps or older devices (like Windows Phone 8 and Xbox 360) that don't support two-step verification.
Hm. "Older devices" doesn't sound like the BB Key2, or BBHub.
Then the page said:
If you have two-step verification turned on and an app isn't prompting you to enter a security code when you sign in, you may be able to sign in with an app password instead.
- 2-setp verication on? Yes
- App (BBHub) prompting you to enter a security code to sign in? No (but then, the Hub never prompts me for a security code when I launch it. My "security code" is entered when I unlock the device.
Another point of confusion: My Google account also is set up to require 2FA, yet the Hub configured my Gmail account without a hitch. In that case, too, the Hub did not prompt me for a security code. Yet I did not need to create anything like an app password; the Hub just loaded the Gmail account, no sweat.
Anyway, thank you again for your diligence in seeing me through this mysterious process.