Game background is black
The black background issue is related to ETS2\ATS launched with OpenGL rendering engine (with startup parameters -rdevice gl) on NVidia graphic cards.
To fix it run the game using DX11.
This is a known issue caused by Overwolf and strictly related to the recording engine. Unfortunately, as Overwolf is using the OBS recording engine, the black background is a side effect. Fixing the black background with OpenGL, the recording engine will stop to work.
OBS has a known problem with OpenGL and works better with DX11 as documented here: https://obsproject.com/forum/threads/obs-studio-does-not-capture-euro-truck-simulator-2.55445/