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After upgrading my laptop (Toshiba Satellite P300 with Mobility Radeon HD 3450/3470) from Xubuntu 19.10 to 20.04, I get a black screen (it does not reach login screen). If I add nomodeset to grub, the screen works but in a wrong resolution (there is no other option on display settings to change to).

What happened during the upgrade, and how can I fix it? Any ideas?

Sumac
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  • While you're in there with the wrong resolution, have you checked to see what video card drivers are loaded? Have you checked to see what happens when you change them? What have you done so far to resolve this beyond adding 'nomodeset'? – KGIII Aug 08 '20 at 21:59
  • @KGIII I could not find anything useful by googling. I haven't checked the driver. How can I see which driver is loaded? – Sumac Aug 08 '20 at 22:06
  • https://itsfoss.com/install-additional-drivers-ubuntu/ – KGIII Aug 08 '20 at 22:17
  • I checked. There are no available drivers to install. My system was working very well before upgrading (there were no additional drivers used). – Sumac Aug 08 '20 at 22:21
  • When I am running "sudo lshw -c video", I get: *-display UNCLAIMED description: VGA compatible controller product: RV620/M82 [Mobility Radeon HD 3450/3470] etc... I don't know if this helps – Sumac Aug 08 '20 at 22:24
  • Have you tried their drivers? https://www.amd.com/en/support/graphics/amd-radeon-hd/ati-radeon-hd-3000-series/ati-radeon-hd-3450 – KGIII Aug 08 '20 at 22:31
  • No, but I prefer using the open source one (since they worked fine). I believe there has to be some setting that got mixed up during the upgrade. – Sumac Aug 08 '20 at 22:35

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If you can get the terminal up then enter

rm ~/.local/share/kscreen
sudo killall sddm

This black screen is legendary (in Kubuntu and Xubuntu) so guuggle it. Check this solution to Kubuntu 15.04 it should work for you too.

darth_epoxy
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  • I emptied the directories (after I backed them up) in home: .cache, .config, .local. Still nothing. – Sumac Aug 09 '20 at 07:23
  • You could be using lightdm or gdm instead of sddm so can you try the "sudo killall" command with each of those? – darth_epoxy Aug 09 '20 at 09:56
  • I cannot get to a terminal on black screen. If I enter through nomodeset then killing lightdm is of no use. – Sumac Aug 09 '20 at 10:37
  • Are you getting grub up so you can choose to boot in recovery mode? – darth_epoxy Aug 09 '20 at 10:40
  • Yes. I can enter recovery mode. – Sumac Aug 09 '20 at 10:52
  • You should have the option to "drop to terminal" and then you can try the kill commands. – darth_epoxy Aug 09 '20 at 11:39
  • If I drop to terminal from the initial recovery screen, then killing lightdm does nothing. The same happens when I am at the login screen. – Sumac Aug 09 '20 at 12:30
  • Sorry that it doesn't work, I had the same problem on both Xubuntu and Kubuntu last year and that got it fixed for me. Do you have any other monitors connected? Make sure you don't. Then from recovery mode you should have the option to "repair broken packages" and if that executes you can resume the boot and you should get the login screen. Once in, go to your driver manager and check for a recommended driver before rebooting – darth_epoxy Aug 09 '20 at 22:00
  • Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/111604/discussion-between-darth-epoxy-and-sumac). – darth_epoxy Aug 09 '20 at 23:53