You (or your new developers) can change the password of a Super User as follows: How do I change the Super User's password when password recovery emails are not sent? - Analytics Platform - Matomo
A Super Users is a user with highest privileges in Piwik, who then can change passwords/email addresses of of other users (or delete and create users).
P.S.: They need to be careful with the password changes though, in case a user’s (who hopefully was specially set up for that) authentication token is used with the Piwik API. Because the token changes with the password: What is the token_auth and where can I find this token to use in the API calls? - Analytics Platform - Matomo, Not user friendly: New password means changed token_auth.