How to enable "Modern Authentication" for MS-Office Outlook 2021 Pro?

Question

Microsoft, on Sep. 26, 2024, will no longer support "Basic Authentication" to access any Outlook account -- they will require using "Modern Authentication". I am trying to understand their instructions found in the following article: Modern Authentication Methods now needed to continue syncing Outlook Email in non-Microsoft email apps

My configuration is Win-10 Pro, Office 2021 Pro, using Outlook 2021 Pro. I have 4+ email addresses using a combination of Gmail and Comcast addresses. Around June 10th, I started encountering random, but repeating requests to reenter my email/password, but only for the Comcast addresses. My searching found the article above, and acknowledged the known issue of repeated password requests. I have a long list of articles I found and have tried their recommendations with no success. Here is what I have tried:

1. The article states: "Option 1: Get a newer Outlook email app which supports Modern Authentication If your Outlook client does not support Modern Authentication, you will need to upgrade to the latest version and then setup using Outlook.com Sync. You can either purchase a new Outlook License, use the Outlook that is included in your Microsoft 365 subscription, or download Outlook for Windows for free." Misinformation from an online chat with Microsoft told me I needed to upgrade from 2016 Pro to newer version, so I purchased 2021 Pro before finding that false (and no refund since digital download!)
2. Multiple articles state the need to add / change Registry Key: Modern Authentication configuration requirements for transition from Office 365 dedicated/ITAR to vNextHKEY_CURRENT_USER\Software\Microsoft\Exchange\AlwaysUseMSOAuthForAutoDiscover and set DWORD value to 1. I did that, plus three other keys mentioned in another article.
3. Is it possible that the Registry Key changes are intended for the Exchange server rather than my PC?
4. Another search found that Xfinity (Comcast) states they support "Modern Authentication", but no mention of my needing to change anything on their end.
5. Other articles mention "Outlook.com", but I don't use that.
6. How to Check Outlook Using Basic or Modern Authentication Connect to Microsoft 365   was useless as the column "Authn" in my Outlook Connections is all blank.
7. I downloaded and installed the "New Outlook", but was really disappointed, so I uninstalled.

Having found articles on implementing "Modern Authentication" that are 4+ years old, I was hoping I could figure this out. Now I need your help!