…so it used to be pretty common in small towns (pre-walmart mainstreet USA) for hardware stores to include a toy department, usually downstairs in the basement, much like how drugstores typically did double-duty as lunch counters…
…the small town where i went to college, though, enjoyed a stereo/mattress/ski shop, and i never wrapped my head around that combination…one of the local grocery stores (pre-hypermarket) also had a full computer department; the most well-appointed amiga retailer i’d ever seen, replete with rendering hardware and video equipment…
…NeXTstep was built on mach and, although i’m unsure if any antecedents remain in macOS, it was certainly production-ready in its day; i remember a couple of decades ago there were stopgap versions of the HURD built on top of mach instead of their own microkernel but i thought that was only ever intended as a temporary workaround…
…i presume on that basis that sustained developer interest was its greatest hurdle, no pun intended…
edit: …is this the post-mortem you mentioned?..