This is an update for my post I made about 6 weeks ago.

I called tech support and they assured me that the version of QB Desktop I'm running will run fine without Internet Explorer. It took a while to get the balls to do it, but I just did. I created a Windows restoration point, installed Windows 21H1 update, rebooted and then started my QuickBooks PME Pro 2019.

It appears they were right, it does work. Even the help system still works. I will update if I run into issues but so far it appears safe to install Windows update 21H1.

IMO it's a big fail on QB's part for not responding in this thread for over a year.