For example, when someone is indicated as a tester, but is no longer part of that Matrix project, you can do the following:

• Make this person a read-only user to the projects he/she should no longer access
• Change the password so that he/she cannot log in anymore (optionally)
• Change his/her email address (optionally)

This way he/she will not be able to log in anymore but you can still use his/her name for documentation.

Note that there are no additional costs for read-only users.

Look at the video (direct link here) on how to adapt the user status: