Using classic Outlook for Windows in business environments
I tried using Outlook 2021 to access my POP3 Outlook accounts and can confirm that it didn't fix the intermittent login issues.
I've decided to use Thunderbird, which works fine and looks a lot better than Outlook 2021 in my opinion. It was a bit of a faff migrating all my emails across (had to use an earlier version of TB for the conversion from the PST file and then upgrade to the latest version of TB) but I think it has been worth it.
With the way Microsoft seem to going I expect I will eventually have to move from Windows as well!