The sys.sysusers view still works in SQL 2019-both on premise and on azure sql. sys.database.principals is a better view with more information. It depends what information you are looking for from the view.
I noticed syslogins view which works in SQL 2019 indicates a user has dbaccess even if it is denied connection to db after creation. There may be a bug in the evaluation version. But I am curious to find out.