Another operating system that deserves mention for 286 class machines is Coherent. This was an Unix like OS you could buy for $99, and it had all of the various Unix utilities and came with a HUGE manual to help you learn it.

They had a 386 version as well, but went all in on getting X-windows and graphics working, and ignored TCP/networking just as the Internet started to gain a lot of traction. Still an interesting OS to look at!