Do you have an Oculus headset? The asset browser seems to cause a crash with Oculus.

If it is Oculus, this thread describes the workaround:

https://steamhost.cn/steamcommunity_com/app/250820/discussions/3/2666626567702041900/

It is! Thanks for the redirect!

No problem. I assumed this was in reference to an environment and not some other game with Workshop integration. Hopefully, that was correct. By the way, this means that you won't be able to simply view your environment after building the map. To work on your map, you'll need to run Hammer Editor without Oculus running. To view your environment, close Hammer, and go into SteamVR as usual. Eventually, your environment will show up in your list of environments, with a message that says something like, "This environment was found on your local drive." You can access it that way and should see any changes from your latest build. It's a real hassle, but it's better than being forced to wait for a fix.

Hmm, the addon is showing up, but when I try to load it in SteamVR, it just goes to the default environment. Do I have to make sure it's fully set up and compatible with SteamVR?

Yeah. You should see it in your list of environments, with a brown thumbnail with the Valve logo. You just use the "visit on my own" button, like for any other environment. It sounds like something's probably not set up correctly. Do you have an info_player_start entity? Were you able to access the addon before the crashes in Hammer started?

Yes, there's a spawn point, but when trying to load the map file normally Source 2 crashes before I can even get into Hammer.

Does it load if you run it from the tools in non-VR mode?

Yep! Source 2 loads fully without VR, likely because it's not having to deal with Oculus or something.

Also, loaded up the map in the engine without VR, and it booted just fine.