The solution to my problem was given to me in #ubuntu on Freenode. Kernel parameter radeon.dpm=0. That's dynamic power management. I think the clue was that everything works fine when the laptop is not plugged in, so the fine young man probably thought there was a bug in dynamic power management. Disabling it allows my laptop to be used now (first time in 6 or so months!). Thank you for your time and energy.
This can be closed. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1855024 Title: Computer Stops Responding Shortly After Logging In Status in linux package in Ubuntu: Incomplete Bug description: I'm using Dell Precision M 4700. I was able to install Ubuntu 19.10 using "safe graphics" mode, but after installing and rebooting into installed system, logging in was successful, but before showing my desktop, the screen continues showing violet or magenta (or whatever that color is), but it has some artifacts in it, and hard drive activity ceases, and nothing can be done except hold the power button until the machine powers off. I am therefore unable to run apport or other bug reporting utilities. Please let me know what I should do to make a better bug report. I searched and I don't think this is a "known issue" or an issue with a known workaround, but if I missed anything, that would be great. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1855024/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp