Interestingly, it seems that the above message(s) have stopped today.
My guess is that MS fixed (behind the scenes), whatever it was that was causing the issue.
I just created a new Outlook account to set up my new phone
Why would you setup and configure an MS account to use on an iPhone?
When I had a Windows Phone (now retired, back in the box and on a shelf) I used my MS Account
On my current Android Phone, I use my Gmail Account
IF I had an iPhone (never gonna happen), I would likely configure an Apple ID (e-mail address removed) or something similar to use
https://support.apple.com/guide/icloud/create-an-icloudcom-email-address-mmdd8d1c5c/1.0/icloud/1.0
Especially if I didn't plan on using it much anyway.
Just seems practical to me, if I'm using a particular hardware platform, to the extent possible I would likely choose to use software, applications, and an environment intended to be used on that platform.