LinuxMint 22.1
Not sure if this is a bug or intended operation but it feels broken.
On a multi-user system, after booting the system (or logging out of all users), the login panel appears but nothing is selectable except the first user. Though it displays the list of users, clicking on any other listed user does nothing until after clicking on the first user and then the panel opens to allow entry of a password (for that user) or selecting other users in the list.
UPDATE: I just confirmed this doesn't happen on LM 21.3. There, every listed user is selectable without having to click the first user.