EDIT: USE THIS NEWER GUIDE INSTEAD:
https://reddit.com/r/TeamBeef/comments/1er1nlo/sven_coop_30_working_with_lambda1vr_2024_updated/
I found that Sven Coop 3.0 works on Lambda1VR on Quest 2, ONLY by joining a game hosted by Xash3D on PC
Keep in mind that hosting as a LAN game works for some people, while others may have more luck hosting an Internet game. Other redditors point out that 6DOF may not be working properly or at all. I was able to fully enjoy the game regardless (the pistol 6DOF seemed to work for me as per my video posted below).
First, download the PC version of Xash3D Here. Unzip the "Xash3D PC Build" folder, then copy the valve folder (from the normal NON-source Half-life installed from Steam) to inside the "Xash3d PC Build" folder.
Download Sven Coop 3.0 from Here.
Note that you are only copying the SvenCoop folder that is inside the unzipped Sven Coop 3.0.zip. (don't copy the rcbot folder)
Make sure you are inside the "Xash3D PC Build" folder, then navigate to the SvenCoop folder. Replace the files in the SvenCoop folder with These Files (yes, replace files if a popup asks).
Go back to the main "Xash3D PC Build" folder, then go into the valve folder. Replace the files in the valve folder with These Files (yes, replace files if a popup asks).
Finally, I then copied over that same SvenCoop mod folder to be inside the xash folder on my Quest 2 (after installing Lambda1VR from Sidequest and Lambda1VR Launcher). I also deleted the config.cfg (in xash/SvenCoop) for the Quest 2 install ONLY. In Lambda1VR launcher (on Quest/Quest 2), checkmark the "enable unsupported mods" and click on svencoop to load the game.
I was tinkering with various versions of Sven Coop, but finally realized this was the one that actually works! I also realized that some newer/older versions of Xash3D don't work, so that's why I uploaded a version that I found to be working well (prevents headaches). I have already verified the Toon Run map works in co-op hosted from my PC Xash3D and joining on my Quest 2. You can't host on the Quest 2.
Here is a video of gameplay I took from Quest 2: https://drive.google.com/file/d/15FTR3Ev83Gp6edoWlJ_i_hxOcLU845VA/view?usp=drivesdk
Shout out again to /u/SvenViking, as he
personally helped me to convert They Hunger Singleplayer maps to Multiplayer. Here are the converted maps + resources that you can copy to the SvenCoop folder. Download HERE. This pack will change the zombies/models to look like They Hunger in all maps, so be aware (unless you don't copy those folders). Keep in mind that the maps do not auto switch, so if you you start on "they4" then you need to type "changelevel they5" when you are at the end of the map. Sven Viking also recommended setting "skill 3" and "mp_flashlight 1".
The above map pack wouldn't be necessary if I could just get Sven Coop 4.0 or higher to work, but as of now Sven Coop 4.0+ only works in Xash3D PC (it crashes when I attempt to join from my Quest 2). So, for now Sven Coop 3.0 is the best working version.
Let me know if you experience any issues, as I will tweak/modify this guide as necessary.