one that i noticed missing: Novell Netware, I spent several years in de 90s developing software for it. It was the main office network server software on those days.
3.x, 4.x ran on relatively regular 32-bit PC server hardware. 2.x ran on the 80286 in protected mode, the only OS I know which did that.
Copies can be found at archive.org.
Are there any any operating systems that you'd like to add to the collection but haven't been able to find?
Maybe someone here at HN could help with that.