I understand your position on W10. While I use it. It is only used for gaming. I use Linux for pretty much everything else due to security & stability.
I do look forward to the day when Linux has full support of games. It's coming but still not there yet.
Have you put a support ticket in? As may need teamviewer session with @Pimax-Support. The support ticket will help notify them of an issue quicker.
Its quite possible there is software conflicting. If your monitor & headset both using native hdmi? If so try connecting your monitor to a dp2hdmi adapter. Display Port uses its own Pathways. Where as the 2 hdmi ports might be causing a conflict.
Not running windows 7 or could test.