Mint users using a non-default keyboard layout (german, french and so on) may encounter an annoying bug regarding the Mint login screen: setting a locale won’t affect the keyboard layout. As result, you can’t login using a password that contains special characters. Logging in using the console still works fine.
So, the first obvious workaround is changing to a console (using ALT-CTRL-F1, for example), logging in and changing the password to another one which doesn’t contain special characters. But this is deprecated since using special characters are an important part of creating strong passwords.
To solve the issue, do the following: open the following file using your preferred text editor:
Go to the last line – it should be
Insert a new line before that last line and enter
for a german localisation. Choose the localisation according your needs, for example fr for french and so on.
Don’t forget to adapt the file again after upgrading to a new Mint version.