Portal RTX.

[I'm Not a Girl]

NVIDIA just dropped RTX for the original game, will this mod also have RTX?

[Supernovae]

Nvidia Lightspeed Studios (not Valve) made the RTX version of Portal 1 using a tool they're still developing called Remix. You can use the first method shown in this guide to get the maps into Portal RTX.
The guide is for getting HL2 into Portal which works surprisingly well because they share the Orange Box version of the Source Engine.
Portal 2 is on a newer version of Source and has a few fundamental differences. In Portal 1 surfaces were portalable by default unless they had the metallic flag. This changed in Portal 2 where surfaces are explicitly marked as portalable so I'm not sure how well the levels would work by default.
I also don't know if the scripts would carry over flawlessly. Had the official RTX remaster been done for Portal 2 instead of the OG, all you'd need to do is copy the assets and vscripts into Portal 2 RTX.

I'm also not sure it would be the best experience to just turn RTX on. Even ignoring potential issues caused from the slightly different game and physics engines, the levels would be too dark without massive modifications to the lighting. This post shows how some levels in Portal look when rendered with raytracing. Definitely stunning but not exactly playable.

I found a video of someone who ported Portal 2 into the OG so it can work: https://www.youtube.com/watch?v=AT5r4CtHsFs

Nvidia Remix[www.nvidia.com] is supposed to launch fairly soon and will make implementing raytracing in DX8 and DX9 rendered games a relatively easy process. The Remix Editor also makes feeding in new textures and assets to replace the old ones extremely easy and I think we'll see RTX mods for quite a few games once Remix is available to the general public.

Edit: Realised Portal 2 uses shaders that aren't currently supported by Remix so it might take some time for newer DX9 games to gain support

[I'm Not a Girl]

Actaul legend