A hypervisor has been detected. Features required for Hyper-V will not be displayed.

The one key setting that must be disabled is the "Memory Integrity" feature which runs a form of virtualization under its hood that Windows 11 detects and will therefore prevent nested virtualization from working. So if you've disabled all Hyper-V components, you'll still have to disable this feature (found under Windows Security), then reboot. You can of course simply re-enable it, once you've finished your nested virtualization session. So, consider it like a mode that you need to 'toggle' between, unless you favour convenience over lower security...