Yes, this is a known limitation when using Teamviewer.
The cause of the problem is this:
When there is no monitor connected to the GSG-8 (or a monitor turned off, or in “power save” mode), the graphics card stops updating the display. So, when we try to connect to the GSG-8, the display is not updated and we can’t really do anything with the GUI.
We have 2 workaround for this situation.
1- Leave a monitor connected to the GSG-8.
The monitor has to be turned ON.
In the Ubuntu Power Settings, the “Blank screen” must be set to “Never”
2- Connect a “Dummy Monitor” DP Dongle to the GSG-8
You can buy those Dongles on Amazon (See link Below)
When you connect this Dongle, Ubuntu will see it as a monitor.
Again, in the Ubuntu Power Settings, the “Blank screen” must be set to “Never”.
Link to an example of a “DP Dummy Monitor Dongle”: