Questions[lxrandr](ubuntu)

I'm using Lubunu 20.04 on a Lenovo X201 laptop. Suppose I do the following:

1. Log in (to a GUI desktop session).
2. Connect an external monitor via VGA
3. Used lxrandr to only use the external monitor
4. Physically disconnect the VGA connector

At this point, the laptop's monitor is dark. Now, Lubuntu - as installed - does not recognize Fn+Monitor Switch keys / does not do anything useful with them. So, I switch to another VT with Ctrl+Alt+Fn (say F2).

I now want to use xrandr to have the laptop display come back on when I switch VT's.

1. Is that possible?
2. When I try to make this work - and I'm no xrandr expert - I fail :-(

Specifically, I tried:

xrandr -d :0 --output LVDS-1 --primary

and it does nothing, and

xrandr -d :0 --output LVDS-1 --auto

gets me aBadMatch (invalid parameter attributes) error. But I don't understand what that means exactly.

Related:

• How to enable monitor from terminal?
• Why do xrandr errors "BadMatch", "BadName", "Gamma Failed" happen?

This has been quite specific scenario but since I haven't found anywhere a single clue how to solve this I thought it's probably not a bad idea to document how I solved it.

Background

• OS: Ubuntu 18.04, deployed with Kiwi builder (rather minimalist build as the goal was to have possibly lightweight system)
• Display Manager: lightdm
• Windows Manager: Openbox

Symptom

Attempt to launch lxrandr from Openbox apps menu gives no effect. Attempt to launch lxrandr from terminal window prints:

    Segmentation fault

Nothing else - no core dump, no other errors, nothing in dmesg or any system logs. xrandr itself works just fine, other visual frontends for XRandR (eg. arandr) worked fine as well. Reinstalling lxrandr did not fix the issue - even though there clearly was something missing, so one would expect that missing bit to be installed as a dependency.

I tried to save my arandr settings to a ~/.screenlayout/default.sh path, but that doesn't work.

Trying different monitors on my freshly installed Lubuntu 18.1 (not by myself only..) it recognized both, but had a stretched picture on the big TV monitor; went to the menu for resolution, it told me a warning when I tried to apply a different resolution, I did not understand.

I saved new resolution and did a restart, ending with a black screen after decrypt and log in. Some other articles tell me here to use Ctrl+ALT+F1 to get a console, but what commands I need to return to normal display since I am a console newbie?

The only thing so far I could find it has to do with xrandr...It is an AMD 64 processor, but graphics card integrated I could not find a proper description in the system info. Unfortunately, I do not remember on which resolution it was, but I think it was 1280x800.

Can anyone help, please?