AMD HD Audio doesn't work with games

This issue makes me crazy because I don't know where the problem is and what it is. The AMD HD Audio works perfectly fine with any browser and music player and video player, but not with any game. Every time I launch a game, the whole audio is cut off and when I quit the game, the audio is working again.

Currently my PC is connected to my TV's HDMI ARC port and the TV is connected to the audio amplifier with TOSLINK. Everything works fine. Then I launch a game and the whole audio system is muted. The audio returns immediatelly when I alt/tab from the game to desktop and cuts off when I alt/tab back to the game. If only one game behaved like this, it would be clearly the game that causing the problem. But every game....

I'd like to use the AMD HD Audio since the Realtek onboard audio is causing intolerable lag and hit reg problems in games. I strugged quite a long time with lag and hit reg issues and one day the onboard audio system suddenly stopped working and at that point the game started to run perfectly without any kind of issues. After that I found out that there is something wrong with the onboard Realtek audio system.

I have done the following things:
- clean installed Windows
- tried different driver versions
- disabled onboard HD audio in bios +Windows HD Audio in Device manager
- updated bios
- deleted every files, registries etc. which says anything A-Volute/Nahimic related
- ran several times sfc /scannow + dism /online.....
- reinstalled games + configured their sound settings
- configured Windows sound settings most likely in all possible ways
- tested all the HDMI ports

Any idea what the problem is and how to fix it?

What does Dxdiag say?
Run it twice, once with HDMI & TOSLINK unplugged and obviously a second time with everything connected.