I really like QubesOS, but you cannot run VMs inside a qube, or other things that require VMs like Docker Desktop for Linux, because the xen hypervisor does not support nested virtualization.
replies(6):
https://forum.qubes-os.org/t/nested-virtualization/14790
Poke around /etc/libvirt/libxl and your particular VM's config file. You'll find some lines like:
<feature name='vmx' policy='disable'/> <feature name='svm' policy='disable'/>
Enable it, and you should have working nested virtualization.