After update, Win10 keeps trying (& failing) to log me in to Microsoft account

I have Windows 10 configured so that I log in to my Windows account, not my Microsoft account.

Last Friday (23 September), I awoke to find that Windows had updated itself, rebooted, and was waiting for me to log in.

But the log-in screen had been changed.  I didn't want that.

I logged in, using my Windows account password, and Windows said "Welcome", indicating that I had logged in to my Windows account successfully.

But my desktop had been changed to the standard Windows 10 default desktop.  I didn't want that, either.

And Windows immediately said that it couldn't log me into my MICROSOFT account, so it was logging me onto a temporary (Microsoft?) account.

I tried to log in to my Microsoft account using my Microsoft password, but Windows responded with the same message.

I thought that maybe I should try to log OUT of whatever temporary Microsoft account I had been logged in to and then try to log in to my Microsoft account, just to make sure I could.  But it turned out I wasn't logged IN to any Microsoft account.

So I rebooted.  But the same whole sequence of events happened again.  Except that this time, there was a DIFFERENT log-in screen.

So I rebooted again, and the "Can't log into Microsoft account" message did NOT reappear.

But now, every few minutes, Windows is saying:

"You need to fix your Microsoft account for apps on your other devices to be able to launch apps and continue experiences on this device."

I don't HAVE any other devices!

How do I make this stop?

First, you don't have your account set up as a truly local account if you're getting this message.  If this message is coming up it means that, at one point or another, the account you're using had a Microsoft account linked with it and that it is now unable to access that Microsoft Account.  If you wish to reestablish the link then open Settings, Accounts, and in the Your Info pane choose the Manage my Microsoft Account link and re-login to the Microsoft Account linked to your Windows 10 account when you're presented with the web browser screen after the link is clicked.

If you don't want a Microsoft Account linked you can either create a new account on the machine that's strictly local and use it or you can try using the "Sign in with a local account instead" link on the previously mentioned pane to convert your account to strictly local (I think it converts rather than creating a brand new account, but I can't say for certain as I've never used this link.  I do have strictly local and Microsoft Account linked Windows 10 accounts on the same machine, though).