I did all the things mentioned in your post, but I didn't install Vulkan. As I am just using it in a hobby project, which I only had time during christmas holidays I probably wait for v72. Nice that it contains the update loader then!
Installing Vulkan worked for me. I am on MacOS 15.1, Unity 6 (6000.0.33f1). I have been trying to get the Simulator working for the past week. Today I noticed that the Hello World docs were updated on 1/16/2025 (see https://developers.meta.com/horizon/documentation/unity/unity-tutorial-hello-vr), so I followed those instructions to create a new Hello World, built it for my Quest 3 and installed it on the headset. That worked, though the new Rig is quite a bit different than the one used in the old Hello World and seemed to be a bit buggy with respect to movement. I did have to do one additional item, which was to go into Project Settings and then Player and set the package name to a standard com.xxxx.xxx, otherwise Meta Quest Developer Hub would say it transferred the package to my Quest 3, but it would never make it there. I suspect I am missing a setting somewhere that is messing up the default package name, because the very first time I did Hello World, the name was fine.
Next, I installed the latest Vulkan from the link above (I installed everything). I could not directly install from the downloaded Vulkan install app. Instead, I had to open a terminal and CD into the app:
CD InstallVulkan.app/Contents/MacOS
And then use sudo:
sudo ./InstallVulkan
Now the simulator launches when I press play in Unity; however, it looks like yet another version of ADB has been installed and so far I have not been able to get the Meta Quest 3 hand controllers to work. The simulator sees the device, but clicking Install Data Forwarding Server brings up: Not Connected to Headset Server, Server Installation Failed. I'll try a manual install of the server next.
A manual install of the Headset Server works and now I can connect the controllers to the simulator, though that often takes several tries. The next issue is that depending on where I set the headset the simulator often says "Conneciton Paused - Check Headset" so I have to keep it close to me, even though I disable the proximity sensor in the Hub. Unclear why. Other than that, the controllers work now in the simulator.
