I'm going to call this complete for now: one Power Macintosh 7300/200, quad-bootable into Mac OS 8.1, BeOS Release 5, MkLinux ("My Kind of Linux" per one of the maintainers) pre-R2, and Microsoft Windows 3.1. Since the PC Compatibility card ☠️ that final one is a bit of a cheat using SoftWindows.
One thing that is made very clear using era-specific hardware: MkLinux is so.... slow... OTOH, BeOS rips. It's so smooth.