Actually Xenix was never a Microsoft branded product.
It was Microsoft's
but they only sold Xenix as OEM'd versions to vendors like SCO and lots
of HW vendors who then added they modifications to support their specific
products (like Apricot, whose machines were far from plain PCs).
Tandy sold a version for the Model 2000, as well as some of
the later TRS-80 badged machines. The Model 2000's version didn't
work well at all and brought to light all kinds of nasty bugs in the
machine that didn't otherwise show up. Most of the later service
bulletins released by Tandy for the machine were geared towards
fixing these bugs under Xenix.
Jeff
--
Home of the TRS-80 Model 2000 FAQ File
http://www.cchaven.com
http://www.geocities.com/siliconvalley/lakes/6757