Do yo get this error?
PDOException: SQLSTATE: Syntax error or access violation: 1231 Variable 'sql_mode' can't be set to the value of 'NO_AUTO_CREATE_USER' in lock_may_be_available()
Then it is a good idea to check out this patch thread: https://www.drupal.org/project/drupal/issues/2978575
I have successfully applied this patch on the dev version of drupal 7: https://www.drupal.org/files/issues/2020-11-17/2978575-290.patch (2020-11-18).
Let me know if you need help with upgrading to upgrade your website from Drupal 7 to Drupal 9.