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I have seen several posts about similar problems, but none that seem to exactly address my particular issue. Until a couple days ago I had been running Ubuntu MATE 18.04.4 LTS on my ThinkPad T460s where I was dual booting with Windows 7. I have a Samsung 1920x1080 monitor connected to the T460s with HDMI and Ubuntu MATE and Windows 7 worked flawlessly with both the 1080p laptop display and the Samsung connected. Since Windows 7 support has ended, I decided to erase my SSD and install Ubuntu 20.04 as my only OS. That installation and the initial testing of my new OS went fine until I connected the Samsung monitor with HDMI to the T460s. Now, when the T460s is powered on, things proceed normally until both monitors display the Ubuntu splash screen. At that point the boot process stops and the Ubuntu name and rotating icon appear on both screens and the boot never finishes. My only choice at this point is to hold down the laptop's Power button to turn the laptop off. If I then disconnect the HDMI cable from the laptop and turn on the laptop, 20.04 boots to the login prompt on the laptop screen just fine and I can log in and get the Gnome desktop. I have done multiple SSD erasures and reinstalls of Focal and the problem always repeats. I have re-downloaded the 20.04 ISO and imaged that to a different USB flash drive and done another clean install. No difference. Debian 10 installed on the laptop works fine with the Samsung connected using the same HDMI cable. I haven't tried any other distros. Sorry this post is so long, but unless this is a just a bug that somehow got past the 20.04 release testing phase I am stumped. Does anyone have a similar situation that resembles this one? Any suggestions or insights would truly be welcome as I really like Focal (Gnome) and want to run it as my daily driver. Thanks in advance! Jim

Jim
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  • Won't help, but I'm running Debian Buster on my T460s. Have to external monitors (DVI & displayport). No problem... Check the differences between both distros. My guess is the kernel... – kanehekili Jul 16 '20 at 20:30
  • When you install Ubuntu - you ought to connect any hardware that you plan to use, including your external display. That way Ubuntu will install everything you need. Also, during installation you should be connected to the internet and "download updates" while installing. You may also need to enable non-free proprietary packages during installation for your display adapter. – Nmath Jul 16 '20 at 22:39
  • I'm seeing this issue on UX32A with Intel graphics and external monitor connected before boot, so can confirm. To debug you have to try booting with edited GRUB kernel command-line string, press <Shift> at boot (before GRUB), press <E> to edit it - change quiet splash to verbose noplymouth INIT_VERBOSE=y (see screenshots here with heading Black/purple screen after you boot Ubuntu for the first time). – N0rbert Jul 17 '20 at 05:49
  • @Jim I have caught the bug on my UX32A with 20.04 LTS and reported it to launchpad as bug 1887916 . You can compare kernel stack trace from bug-report with yours. – N0rbert Jul 17 '20 at 10:06
  • @all Thanks so much to everyone who has taken the time & trouble to comment & test, especially to N0rbert for confirming the bug and submitting it to LaunchPad. Since my original post, I have clean-installed Ubuntu MATE 20.04 as a test. MATE 20.04 has no problem booting, and operating, with 2 external monitors. Today I booted into the 20.04 GNOME installer with both external monitors connected. I chose the live "Try Ubuntu" option for this session, and all 3 monitors were active and behaved as expected. Is the problem with the GNOME desktop that ends up being installed with 20.04? – Jim Jul 18 '20 at 17:36

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