We consider physical desktops all desktops that are either really physical (in the sense that they are running on physical hardware) or that are running as physical desktops inside a virtual machine. Any of our server products perfectly fit this scenario, and that includes the free version which permits access to the physical display.
Your screenshot shows KVM running Debian instances, but these virtual machines could be any of the other supported operating systems, so Windows and Mac, running inside VMware, Xen, among others and even in a Docker container. You configure and run NoMachine inside such VM instances as you do on a physical computer.
The question here is not a technical one, rather a licensing one. The free version is for individual use (and that can be in a private or work environment). Section 2. GRANT OF LICENSE AND TERMS OF USE of the EULA is quite clear about how it can and can’t be used. https://www.nomachine.com/licensing-5. If your scenario doesn’t fit into the use cases that we describe in a) and b), I suggest you contact the sales team to get further guidance. Click Contact Us in the footer of the website and select Sales Enquiries.