Just to make sure, I again repeated the sequence of events outlined above on the stock 17.10 kernel:
Linux magpie 4.13.0-16-generic #19-Ubuntu SMP Wed Oct 11 18:35:14 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
The behavior is identical to that reported above.
One minor elaboration: when I open the control panel->Devices->Displays with the lid action set to "ignore", I have to toggle the external monitor, even if it is currently selected, in order to prevent the lid close from blanking the display.
Just to make sure, I again repeated the sequence of events outlined above on the stock 17.10 kernel:
Linux magpie 4.13.0-16-generic #19-Ubuntu SMP Wed Oct 11 18:35:14 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
The behavior is identical to that reported above.
One minor elaboration: when I open the control panel-> Devices- >Displays with the lid action set to "ignore", I have to toggle the external monitor, even if it is currently selected, in order to prevent the lid close from blanking the display.