After I first tried to create a macOS 27 VM on macOS 26, I remembered that for prior major releases you needed to install the Xcode beta in order to install the beta into a VM. So, I installed the Xcode 27 beta on my host. Now, I can no longer create Tahoe VMs on my Mac. (I was going to upgrade the VM to Golden Gate through Software Update.) What do I need to do to revert the state of my Mac to the point where I can create Tahoe VMs again?

Well, as someone who only has a single Mac, I prefer to use VMs to test my software against new releases. I know I can create a second boot volume to run the beta but that's really quite inconvenient. So, count me as very interested in a better workaround.

You need to install the Xcode 16 beta. It has the required updated components to allow the installation. Before installing Xcode 16, I got the same error trying to install Sequoia using UTM. After installing Xcode 16, UTM was able to install Sequoia.

Someone using Virtual Buddy discovered a way to enable updating a Sonoma VM to a later beta release. I tested it myself and it works although you may have to refresh the Software Update panel a few times before it sees the later beta. Apparently, it's a one shot deal. To update to a subsequent beta, you have to run the script again. Here's a link to the script.