I successfully used Séb’s instructions to install WSL in a Windows 10 virtual machine in VirtualBox, but I then failed to upgrade it to WSL2.
WSL2 runs in a virtual machine, so for this to work in a Windows 10 VM, nested virtualization needs to be enabled. I did enable it in my VM’s configuration, but this didn’t seem to make a difference.
I know others have had better luck using kvm and virt-manager. I’ll continue poking at it when I get a chance, in the meantime if anyone has encountered the same problem and has managed to solve it, I’m all ears!