QEMU

With QEMU, you can safely explore the entire landscape of operating systems in isolated virtual machines. This free virtualization software emulates entire computer systems, including CPU, memory, and peripherals, allowing you to boot everything from Windows and Linux distributions to BSD and niche research OSes. It's the perfect risk-free way to compare features, test drive potential replacements, or learn system administration. Since it's open-source, you have complete transparency and control, ensuring a secure testing ground for your evaluations without licensing costs or hardware modifications.