After getting the login -> black screen -> login loop I created a new macOS 10.5.5 VM. This time I created a second standard user account that does not have an apple id associated. After upgrading I am still getting the login loop on my main-appleid tied account but I can login into that standard account just fine. Could it be something with looking up appleid information on login? I'm looking through the log files from the other account and have not found anything yet.