Gregory's Server@stefano Yggdrasil in 1993 (Linux kernel 0.99). After that SUSE, mostly because you could buy it as an offline 6 a 7 CD box set (ComputerCollecfief in Amsterdam!) so I could take it with me to Africa where I worked at the time and internet access was…challenging. These days Kali in a VM on a Mac Studio. Reluctantly a (licensed) copy of Win11 in a VM just because old electronics test equipment only come with, mostly terrible, windows software.
@Bleijswijk Keeping a copy of Windows around for some, specific uses is more or less normal. My home alarm system software can be programmed only from Windows (Wine doesn't work with it). So I have to keep a Windows installation for this. And, I must admit, for the few times per year I have time to play some games. 🙂