Why not to run Docker containers from within a Hyper-V virtual machine?
Well, when you are trying to install Docker Desktop for Windows, it installs correctly. But running it will prompt you about Hyper-V is required for Docker to work.
Programs and Features on its turn shows you that Hyper-V is greyed out, so you cannot install it from there
Not everyone knows, but Hyper-V in fact allows having nested virtual machines. That means running docker is also possible from within a VM. All you need is just running one PowerShell command from outside of your container:
Set-VMProcessor -VMName _YOUR_VM_NAME_TO_ENABLE_ -ExposeVirtualizationExtensions $true
What it does - just adds virtualization features into a virtual processor of outer VM, similar to those you got at you physical CPU. Thus you need to run this command of the VM switched off.
Once done, Sitecore perfectly builds and work if Docker running within a virtual machine. For those who are total beginner and scary to mess the things around their host machines - this could be an option. However there is of course a performance penalty from double virtualization.
Finally, the main trick! Just because you've added virtualization extensions into a virtual processor of your VM, you may run docker in process isolation mode, relatively to the build number of VM's operation system. Will explain it on the following example: imagine, your host machine runs Windows 10 build 1809, but got no problems of running Windows 10 build 1909 in a Hyper-V machine there. Now, you after you enable virtualization extensions to that virtual machine (that runs 1909), you will be able to install docker within that virtual machine, and run 1909-built images in process isolation, natively to that VM: 1909-built images run on 1909- machine! But at the same time you will be able to run those same images only in hyper-v mode on the (outer) host machine, because it has 1809 and cannot run non-matching images in process isolation mode.
Hope this helps!