I have a Win10 Lenovo Thinkpad. I want to switch to Linux, but I'd like to keep my Win10 system. Is there a way I can install a VM underneath this pre-installed Win10 system, so that I can still launch Windows while I'm transitioning?

Installing a VM, and then installing licensed Windows over that, isn't an option, because I don't want Win11, and you can't buy Win10 licences any more.