Outlook 2016 doesn't accept password or app password

Mobile - latest Outlook for Android, and latest Gmail for Android,

Personal - Outlook 2013 with latest updates all installed and OAuth regkey added

Work - latest Outlook that is a part of M365 as of this comment, build 2308 / 16731. I attempted this but was getting constant prompts, so much so that it was disrupting my work flow, so I removed the account from my work Outlook.

Not installed any more but have attempted in the last several weeks:

Thunderbird for Windows

Latest Outlook for iOS

Gmail, not a single issue over the same 4 weeks, even over my work travel.

As far as account setup is, I've tried to the 3 methods:

1. Use Microsoft Exchange type if it's explicitly listed, if not, then
2. Outlook.com type if it's listed; and
3. Auto discovery based on email address if the other 2 fails.

I did start removing my Hotmail/MSN/Live mail accounts from my devices - because the constant pop and associated alert tone was driving me nuts!

What version of Outlook are you running against? What I can confirm is that OAuth is only supported for Outlook.com in the versions that I mentioned in the latest known issue post. While OAuth bits and registry keys may have been in earlier versions, that does not mean it is supported for all account types. The official supported versions for Outlook.com is indeed what is listed in the known issues.