NM…at some point I must have deleted the line with Set-PSUAuthenticationMethod from the file. Using the code examples from the Security page, and copy/pasting them were not working. This article explained that issue: Authentication.ps1 - convert to type "PowerShellUniversal.AuthenticationMethod" - #5 by adam
The documentation expects you to be editing the file from within the UD Admin page Settings \ Configurations. There you don’t work with that line. Working directly in the file, you need that line. LOL
Wrapping everything inside the script block of this command fixed it for me: Set-PSUAuthenticationMethod -ScriptBlock {}