Turn laptop monitor back on from another VT, after disconnect from external monitor

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?