Acorn had a BSD-derived Unix offering, and there’s an interesting thread over on Stardot:
Who was using RISC iX back in the day?
As often the case, paulb delivers some links to interesting articles:
…how could I forget Solaris and SunOS on x86?! Here are some Byte articles of potential interest from the era:
“Sun’s New Workstation: the Sun386i”, Byte, July 1988.
“Two Powerful Systems from Sun”, Byte, May 1989, featuring the Sun-3/80 and SPARCstation 1.
“Some Flavors of Unix”, Byte, May 1989
A nearby thread will help you get started, perhaps using Arculator:
How to run RISC iX for yourself!