for the installation of matlab on fedora34.
To solve the issue with the "login name" I´ve clicked in the input field for the login name.
Then I used the shortcut
to switch to the right workspace and
to switch back to the installation workspace.
Now you should be ready to write your login name in the input field and finish the installation process.
Note, that you can define any other shortcut in the "settings" - "keyboard options" for switching of the workspaces, if the upper shortcuts are not working.
It worked fine for me and I hope for you as well.