I believe I'm experiencing this issue as well. If lightdm loads up, I enter half my password and the flickering happens, I type the rest of my password and am not able to login. I believe the flickering interrupts my typing somehow. When I retype my password entirely after the flickering, it works fine.
Ubuntu MATE 16.04 Ubuntu MATE desktop 1.12.1 CPU: Intel Core i7-6500U CPU @ 3.1GHz GPU: Mesa DRI Intel(R) HD Graphics 520 (Skylake GT2) -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to xserver-xorg-video-intel in Ubuntu. https://bugs.launchpad.net/bugs/1531224 Title: lightdm-gtk-greeter flickers once little after lightdm starts Status in LightDM GTK+ Greeter: New Status in xserver-xorg-video-intel package in Ubuntu: Confirmed Bug description: Bug context: · Arch Linux x86_64 4.3.3-2-ARCH · systemd 228-3 (using lightdm-plymouth.service) · plymouth 0.9.2-8 (compiled from AUR) · lightdm 1:1.16.6-2 · lightdm-gtk-greeter 1:2.0.1-2 At the end of boot process, right after plymouth splash, lightdm starts normally and the GTK+ greeter login screen is shown for about 1 second, but then the screen instantly flickers (goes black) and the greeter is redrawn. From here on, everything works flawlessly, but the brief flickering is certainly annoying. This happens every time and no other greeter I have tried presents this issue, so I can confirm it is lightdm-gtk-greeter-related. To manage notifications about this bug go to: https://bugs.launchpad.net/lightdm-gtk-greeter/+bug/1531224/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp