The game is using shared resources for the UI (D3D11 from QT -> D3D9 in Source) which is something we cannot support right now.

The game is also missing some synchronization for these shared resources given it flickers all the time for me on native DirectX on both AMD and Nvidia.

As a workaround you can use -useoldgameui which will also be much faster...

Can you please send me what I need do with command useoldgameui. I have steam version Black Mesa, and I have some problem when I start game with Proton 5.0, my game have not menu, and I can't start the game.

As a launch argument in Steam.

Joshua, thank you, but i still not sure, all i do correct. Could you look my screenshots?

If you can see, this way do not halp me.

May be you know any ways?
Thank you.

You need to prefix the option with %command%, which represents the Proton + game command. Like this:
%command% -useoldgameui

Aqxa1, thank you, I will try this way today in the evening. And i am going to send about result as soon as I try this way.

The correct launch argument is -oldgameui.

So it is very interesting, I think I will try all ways

So, i tried different ways, and in my case i had good result when i used %command% -oldgameui. Anyway, thanks everyone for help.

https://youtu.be/mDa4XNHf0vY
Also issue with dynamic lighting, red lightning from any dynamic light source

Hello, as always thank you for your work and time.

Is there any hope for this working some day? The old UI has a problem with high resolutions (doesn't scale) and the native port is still... well, we use Proton on this game for a reason after all.