Discord User Gistix on the Flatscreen to VR mod team has released a video showing further development on porting the L4D2VR mod to Portal 2. Keep in mind this is a mod of the game not using the source code so there are a lot of things that are just not possible without access to the interworking of the game itself. We will continue to watch the progress of the mod.

May 28, 2023

I think they could switch to Portal 2 Community Edition. It's a mod which updates Portal 2's engine with features from csgo and source 2013. The team is giving beta access to it on their discord I think P2CE will give more access to code and things than the default portal 2 version, though I'm not an expert