The 80286 is a very old chip. In that era there were no free versions of unix available. But there were products that you could buy. Microsoft and SCO were fiddling around with a unix clone called XENIX. They ported XENIX from the 8086 to the 80286 with little trouble. The 80286 was the chip that powered the IBM PC/AT. Intel and the Unix Support Group managed to port System V Release 2 to it. The was the only multi-user capable UNIX port to the 80286 and it "will support 2 or 3 users fairly well" (1).
No modern version of UNIX has any chance of running on a 80286. To compete, all modern versions of UNIX will have features like demand paging and shared libraries. Features like that require a gizmo called a Memory Management Unit. And the 80286 doesn't have one. I have no idea where you can obtain a copy of either XENIX or System V Release 2 for the 80286. And remember, these were products. You had to pay for them.
Sorry for the bad news. Maybe you should upgrade to an 80386
1. Most of this info came from
UNIX Papers for UNIX developers and Power Users, edited by Mitchell Waite 1987 ISBN 0-672-22578-8, Chapter 11
A UNIX Port to the 80286 by Anthony Andrews.