Good troubleshooting — and your lightdm --show-config output is actually the key clue. autologin-user and autologin-user-timeout=0 are exactly right, so autologin is configured correctly on that machine. LL8.0’s autologin also doesn’t depend on being in any special group, so you haven’t missed a setting.
That’s why this isn’t really an “autologin didn’t save” problem. When the config is provably correct but only one specific machine still lands on the password screen, what’s almost always happening is: LightDM does start the automatic session, but on that hardware the desktop session fails to come up (typically a graphics-driver hiccup) and LightDM falls back to the login screen. The result looks identical to “it asked for a password,” but the cause is the session, not the setting. That’s also exactly why the same ISO autologs in fine in a VM and on your other machines — different GPU/hardware.
To confirm, on the machine that prompts, log in and post the output of:
Code:
cat /var/log/lightdm/lightdm.log
cat ~/.xsession-errors
loginctl list-seats
The lightdm log states plainly whether it attempted the autologin and what happened to the session afterwards; list-seats shows whether a second GPU created a second seat (another known cause of this exact symptom).
While you’re in there, two quick checks on the failing machine:
- ls -l /etc/lightdm/lightdm.conf.d/ — the autologin setting lives in lightdm-autologin-greeter.conf. Make sure nothing else in that folder also has a [Seat:*] block that could override it.
- If the machine has switchable/hybrid graphics (Intel + NVIDIA/AMD), that’s the prime suspect. Try installing (or removing) the proprietary driver via Lite Driver Manager and retest.
Those three log outputs will tell us exactly why this one box behaves differently from identical installs everywhere else.