I have no idea what package handles the login. According to the wiki (https://wiki.ubuntu.com/Bugs/FindRightPackage) if one encounters a bug at the login screen, the package is the display manager, which is LightDM in Ubuntu 11.10 or above.
** Package changed: ubuntu => lightdm (Ubuntu) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1769416 Title: Can't login on 18.04 after entering wrong password To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1769416/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs