Go to Menu> Settings> Components> Scroll down to Do Not Disturb Mode and disable it.
See if that makes a difference and report back.
I'm back with news.
Unfortunatelly I don't have much information to give. All I can say is that I disabled 'Do Not Disturb Mode' and started a game which created issues. The game didn't alt+tab itself anymore.
Then I did the following:
- Closed the game, re-enabled Do Not Disturb Mode -> Start the game -> No issue (I found this strange)
- Restarted the computer -> Start the game -> No issue again
I'm not sure if only disabling / enabling this feature fixed my problem or just disappeared itself. I'll keep watching anyway. If the problem will appear in future, I'll try to test these configuration and come back. If I will not have anymore this issue, you won't see any reply from me here :-)