• Portal 1 license and installed Portal With RTX
• Garry's Mod
• https://github.com/robotboy655/gmod-lua-menu

First of all, we reset Garry's Mod and disable all addons (except maps)
GARRY'S MOD VERSION SHOULD BE STABLE!!!! WITHOUT CHROMIUM AND x64!!!!

We find the Portal With RTX and find its location
Next, go to the bin folder and copy the following files/folders from there :

===
.trex
d3d9.dll
dxvk_d3d9.dll
NvRemixBridge32.dll
stdshader_dx7.dll
stdshader_dx6.dll
===

We transfer them to the bin folder in the Garry's Mod directory

We set ourselves a Lua menu by the link from GitHub (I think they are not stupid and you will figure it out for yourself

Now go to the following file: Garry's Mod/garrysmod/lua/menu/menu.lua
Open it with any editor and delete this line: include( "loading.lua")

Open the folder with Garry's Mod, find hl2.exe and in the same folder, tear off the console and run hl2.exe as follows:

hl2.exe -dxlevel 70 -w 1920 -h 1080 -condebug +mat_dxlevel 70 +mat_disable_d3d9ex 1 +r_worldlights 16 +sv_cheats 1 +r_frustumcullworld 0 +c_frustumcull 0 +r_occlusion 0 +r_forcenovis 0 +r_shadows 0 +mat_lodwarelighting 0 +r_staticpro +r_vertexlighting 0 +mat_queue_mode 0 +r_unloadlightmaps 1 +mat_drawwater 1 +r_glint_alwaysdraw -1 +mat_softwarelighting 0 +r_3dsky 0


And so, I will say right away that standard cards do not work (it will paint)
download another map (for example, BigCity) and go to it through the menu

We went in, but that's terrible!
Everything is black!!!!!

We fix it...

Open the chat in the game, then press Alt + X
In this window, click on Developers Settings Menu

From the top right, open Game Setup
Next, we are looking for Sky Textures

Now we see a lot of textures, look for everything that looks like a skybox and click!

It works very unstable ...
Crashes quite often, but it's quite interesting to run around the maps)))

I took the information from: https://www.youtube.com/watch?v=Epx3qjlJdtA&t=0s