In case you were wondering, you can easily run macOS 15 in a VM by downloading the IPSW from developer.apple.com and using it to create a new machine in VirtualBuddy (https://github.com/insidegui/VirtualBuddy). Thanks @_inside for your continued work on this!
GitHub - insidegui/VirtualBuddy: Virtualize macOS 12 and later on Apple Silicon, VirtualBuddy is a virtual machine GUI for macOS M1, M2, M3, M4

Virtualize macOS 12 and later on Apple Silicon, VirtualBuddy is a virtual machine GUI for macOS M1, M2, M3, M4 - insidegui/VirtualBuddy

GitHub
@chris @_inside Does this still have the limitation that you cannot use AppleID (…developing in Xcode, iCloud) withing the VM?
@hannesoid @chris @_inside According to Apple’s documentation it should now be possible to use an Apple ID as long as both host and guest run macOS 15. Has nothing to do with VirtualBuddy, though.
@softmaus @chris @_inside nice, then probably from macOS 15 release on we can develop in a beta-os VM within current-os host
@softmaus @hannesoid @chris @_inside I'm hoping this means could run iCloud Photos in a VM on an external drive. I want to do "Download Originals" so I can do a full backup, while I do "Optimize Storage" on my host 512GB Air. I keep an old 2017 iMac around for this purpose, but it takes up space and I don't need another desktop Mac. Maybe there are solutions to this problem, but haven't found one (e.g. tried icloudpd)