EUL - Easy User Login
With Easy User Login, administrators can log into other user accounts in the frontend. The plugin adds a login button in the overview of the User Manager in the backend. Both core templates (Isis and Hathor) are supported.
After the login, the logged-in administrator can perform all the actions that the user can do with his normal login. For security reasons, only users from the 'Super Users' group can initiate the login process. In addition, the login cookie is used to check whether the user is still logged into the backend.
The plugin is useful to test functions in the frontend or to perform actions for the user that are not directly possible without a login. The login is only possible in non-blocked accounts!
Joomla! 3.x - https://joomla-extensions.kubik-rubik.de/downloads/eul-easy-user-login/joomla-3
The extension is completely free, but you need a subscription for support: