I have Kubuntu 20.10.
I have Steam.
I installed the precompiled binary of MangoHud.
It is pretty nice software.

For Bioshock Infinite, there is a bit of pain in the butt where textures pop and it uses LOD on the models and there is popping all over the place.
The EXE thinks that the system has 400 MB of VRAM.

The solution to that is
/home/<user>/.local/share/Steam/SteamApps/common/BioShock Infinite/XGame/Config/DefaultEngine.ini

Find the line with
PoolSize
The value is in MB. For example, if you have 4 GB of VRAM, input 4096.

From Steam, you have to right click on the game
a popup menu appears.
Click On Properties
A window opens up
On the left side, choose Generalizing
On the right side, at the bottom, it says Launch Options.
Enter
MANGOHUD_CONFIG=full mangohud %command% -ReadTexturePoolFromIni

At the top right, click the X to close the window. There is no OK button.
Launch the game.
Whenever you change the DefaultEngine.ini file, you have to go into Options and set the Graphics Quality to ultra.

~~~~vmelkon