Installing older macOS says "unable to detect operating system"

I have a MacBook Pro and I'm running Big Sur. I'd like to install either Yosemite or Sierra as a virtual machine. I downloaded the .dmg files but when I try to install them it says "unable to detect operating system." Customer support told me that I need to use an .app file, not a .dmg file. I tried searching for MacOS .app files but I can't find them. Does anyone know where to get them? Or is there a way I can use the .dmg file? Thanks.

 

Hi, according to your comments, you've already found the solution. Could you share it here please? Maybe it will be helpful for other users.

 

Sure! I opened up the .dmg file and installed it. After it installed, it created an .app file in the applications folder. I used that .app file when creating a new macOS virtual machine in Parallels and it worked. Hope that helps anyone else who was having this problem!

 

Install macOS from Scratch · Apple Silicon (M1 chip and newer): Press and hold the power button until you see the startup options window,

 

If you try to install a macOS that is older than the version currently installed, the installer will say that it is too old to be opened on.

 

it says "unable to detect operating system" then if ... r/mac - Just got me my first MacOS device after 16 years on PC.

 

I have a MacBook Pro and I'm running Big Sur. I'd like to install either Yosemite or Sierra as a virtual machine. I downloaded the .dmg files but when I try to install them it says "unable to detect operating system.