Desktop image cannot be unlocked

[basak]

Required information

N/A (this affects a published image and not lxd itself)

Issue description

The image provided by images:ubuntu/24.04/desktop seems to default somehow to locking the screen, and also allows the user to lock the screen manually, but then unlocking requires a password not known to the user.

Steps to reproduce

1. lxc launch --console=vga images:ubuntu/24.04/desktop --vm -c limits.cpu=4 -c limits.memory=4GiB
2. After boot, inside the desktop environment press Super+L
3. Try to unlock from there.

I actually encountered this by coming back to find that the desktop session inside the VM had locked itself. I'm not sure how. In that case I was being prompted for both my username and my password, rather than just my password.

Expected behaviour

• Super+L should either do nothing or blank the screen in some way that does not require a password to unlock unless I actually set one myself.
• If the session goes into some kind of lock mode by itself, this also should not require a password to unlock unless I actually set one myself.

Information to attach

N/A

[basak]

Discussion thread: https://discourse.ubuntu.com/t/cannot-unlock-default-desktop-image/46446