I have tried setting up my gmail account as POP on two computers. My Mac Desktop is still on Catalina Version 10.15.7 and Microsoft Outlook is Version 16.43 (20110804). On this computer, I have my personal gmail account setup as POP and there are no issues. This was established way back when I originally installed Microsoft Outlook for Mac 2011. I recently upgraded to Microsoft 365 and my email accounts didn't have any negative impact at that time. I've not switched to the new version of Outlook on this computer because I read that POP doesn't work with this release. When I attempt to setup a new gmail account as POP, it doesn't work. My configurations in gmail are exactly the same as the other gmail account that does work.
My MacBook Air has been upgraded to Big Sur Version 11.1 and Microsoft Outlook is Version 16.45 (21011103). If I try to add my gmail account as POP, I receive the same error message as I do with my Mac Desktop (noted above). If I switch to the "New Outlook" format, I don't even have the option of selecting POP. The only accounts supported are Office 365, Outlook.com, Google and iCloud. That same pop up window shows COMING SOON: Exchange, IMAP, Yahoo. So, I essentially cannot move to the "New Outlook" format because my personal company uses an Exchange Account for all of my contacts and calendar.
A couple of things to take note of: 1) I use an Exchange Account to capture my calendar and contacts because a few years back, Microsoft stopped supporting the sync capability between Outlook and iPhone. I had to use an Exchange Account if I wanted to continue to use Microsoft Outlook to capture my contacts and calendar and have that sync with my iPhone. 2) If Microsoft is going to release new versions and "new" looks of Outlook, then they should be sure that it works with customer configurations. Right now, I cannot setup a POP email account on the old look of Microsoft Outlook and it's not even an option in the "New Outlook", and I'm not sure if this will even be available. I also am not able to use my Exchange Account until Microsoft enables that feature in the "New Outlook".
Super frustrating to say the least.