Just an update. As of this morning, it appears that the read status of messages is "sticking" in my new Outlook client. I have made no overt changes (though background updates are always a possibility, as I am a bit obsessive about keeping my systems patched...)
Definitely not my case, Windows 11, Microsoft 365 (enterprise), both up to date as of today.
Still the same issue, the 'new' Outlook and Gmail are not syncing read/unread status.
I am the user who posted the workaround instructions on page 2. That is still the only way to keep my Outlook synched with Gmail. And still an unacceptable way for an enterprise-level email app to work.