To run mafia with RTX Remix you need:
Correctly set settings in setup.exe from the game folder (the settings are shown in the screenshot)
Copy Remix Runtime files to folder with other dll's, A1.dta, A2.dta and so on
in the .trex folder put the bridge.conf, which I dropped below, also in the main folder with all the dlls rename the original d3d9.dll to d3d9.remix.dll and put my d3d9.dll and d3d8.dll, which I attached to the #1055103037271703602 message, in the folder
in the developer menu, go to the game settings tab, expand UI Textures, and click on all interface textures, then expand Sky Textures, and click on all sky textures
After these steps, the game should work
2000s games sometimes had open source, like rtcw