Thanks very much for the answers. Glad to hear that a gaming computer works with free software.
Unfortunately I have no physical access to free hardware such as System76 and related. Even weak hardware I now use is non-free. I just deemed ADM Ryzen a less of two evils in this regard, but I may mistake. So what I am looking for is gigabyte Ethernet, nested virtualization, clear desktop performance, I can endure lack of wifi, I don't need games, so no need in fancy video card, instead I need CPU for mass calculations and heavy software being built and tested all the time on many virtual machines at once (at once because these machines will interact with each other). So I am going to organize something like Qubes on my desktop.
