I know this is software focused, but as much of the work done in DOS 2.0 was to support the introduction of hard disks, it would be worth mentioning what the hardware was in the PC/XT:
2BSD is still hanging on getting updates and forked projects to this day. My understanding is that it's longevity in the face of the existence of 4bsd is because it is 16-bit clean, These days it is manly for people who want a unix for their microcontroller.
https://github.com/microsoft/MS-DOS/blob/main/v2.0/source/CO...
https://en.wikipedia.org/wiki/ST-506/ST-412
https://www.google.com/search?client=firefox-b-d&q=ST-212+ha...
Interesting. At my old job I got my hands on Wang IN/ix around 1985, a 16 bit UNIX.
It ran on an 8086 but needed 512k memory. It ran I wonder if memory was the main issue ? But seems the issue was probably memory.
Here is one, https://github.com/RetroBSD/retrobsd. This is for the pic32, so I may be wrong about the 16-bit thing.
I don't know if anyone has done it but it looks like it could fit, perhaps not on a original 8086 PC, but perhaps a 286 with 640K.