TB opens in the folder that was open at last closing. If it doesn't, Help/Troubleshooting, click Open Folder, close TB, and delete session.json. The Manually sort folders add-on has an option to set the folder that is open at startup, no matter which one was open at closing.

I installed the add-on, but all it helped with is the order of the accounts. The account (currently the 2nd in the list) always gets the focus when Thunderbird opens. It doesn't matter where it is in the list. Also, I have selected the inbox that should get focus when the app opens, but it still opens on the 2nd account's inbox.

Did you delete the json file and see if TB opened with the last folder, before you installed the add-on?

Yes. There was no change in the behavior.

See if the last opened folder is remembered when you start and close TB a few times, but in safe mode (hold Shift when you launch TB).

Yes, I did try safe mode. I decided that I don't have anything in Thunderbird that isn't on the email servers so I uninstalled, remove profiles and reinstalled. I didn't have any add-ons installed, so nothing to worry about with those. I'm sure there were a few tweaks to account settings, but nothing earth shattering. Thanks for your suggestions and help.