What I did was download the legacy physx and rename it to the one in the redistributable folder and delete the original one. Then install the game with steam normally.
LOG:
steam-21680.log
Crash at startup about PhysX

Crash in application version: 1.1.0.12714
This game requires an up to date version of Ageia PhysX and associated DLLs. Please install latest PhysX runtime.
SYSTEM:
CPU : Intel(R) Core(TM) i3-8145U CPU @ 2.10GHz (2 cores)
DirectX : 9.0c
Memory : 9725 MB
Physics : normal
Renderer : DX9 threaded
Sound : ()
Note: PhysX is still needed, but game currently crashes without any visible windows showing in current Proton Experimental.
A workaround would be using GE-Proton7-20 (last working version, as 7-21 and above exhibits same crashes), but the sound has some subtle but noticeable artifacting rendered as a small audible buzzing at times.
In addition to manually installing PhysX, you also need to change the launch command to taskset -c 0-14 %command%
I can't make this game to boot with Proton 6, 7, 8.0-5, 9.0-2 or Experimental (2024/06/28). I've tried the suggested fixes above (installing physx with winetricks and WINE_CPU_TOPOLOGY=4), but nothing works.
Proton log:
steam-21680.tar.gz
Specs
I was able to launch this one with Proton 10.0-1 (beta-f) using the following workarounds:
21680) in case you have already tried to launch it.%install_dir%/Bionic Commando Rearmed/Support/PhysX.PhysX_7.11.13_SystemSoftware.exe) present in the folder.PhysX_7.11.13_SystemSoftware.exetaskset -c 0-14 %command% (WINE_CPU_TOPOLOGY doesn't work here)Specs:
P.S: workaround still needed for Proton 11.0 (beta)
Hoping I'm adding this to the right place.
With the new 3.8 steamOS update the screen is now squished in the top left corner and has no sound. The squished screen can be fixed by going into desktop mode and changing to windowed mode but the game itself still launches in gaming mode with no sound or controls. Desktop mode is unaffected.
This worked just fine before 3.8, obviously with the taskset launch command and correct physx installation. Is there a way to fix this on gaming mode back to where it was working correctly before?
proton 10.0-1x1 2025-05proton 11.0x1 2025-05ge-proton7-20x1 2022-07proton experimentalx1 2022-07WINE_CPU_TOPOLOGYx1 2025-05WINE_CPU_TOPOLOGY=4`),x1 2024-07
Compatibility Report
System Information
I confirm:
steam-21680.log
(Please note, the above log file was generated after I had already followed the corrective steps listed below to get the game running.)
Symptoms
The game fails to launch due to missing Physx library.
Reproduction
Just try to launch the game with its vanilla prefix. You'll get the popup error window telling you it couldn't find the Physx library.
Current Solution
protontricks 21680 physxSTEAM_DIR="/path/to/dir"