The underlying Lightning APIs always honor field level security, and the conditions are checked locally on the client, rather than the server, as it was in the Classic UI. The net result is that the user must be able to view the field in order to have the conditions be checked properly.
User License assigned to a permission set can’t be modified after the permission set is created.
Please check the below link for more information https://help.salesforce.com/s/articleView?id=000332257&type=1
You can use Lastmodifedby field to identify Who attempt to change the username, but it's also not work when the user account receive more update on that day.
But there is an object called Setup Audit Trail in Salesforce. You can use that object to identify which user change the username for the specific user record. Please revise this blog to know more clear ...
This error msg means that query did not return any results, and you are trying to assign this to SObject. It could be either this line
Profile p = [select id from Profile where Name = 'System Administrator' limit 1];
Or somewhere else in the TestDataGenerator.createAccount(true).
When you are deploying a change set, you can choose to run just a specified ...
You simply need to ensure that this "integration user" is set with the "API Only" permission:
API Only - Specifies that the user can only log in through the API. This prevents the user from being used for any purpose other than integration scenarios
I understand you are not using record types,
but are you sure there are none created check in object manager just being cautious?
And if there are none just in the list view filter set recordtype equals blank (its mentioned in the docs)