SIMH is a good emulator for 70s-80s minicomputers. The Unix heritage society (TUHS) has a lot of software, including early Unices, at their Unix archive. Some of it is a little tricky to get to work, but v6 and v7 Unix both work like charms in my experience.
Edit: This article (https://connect.ed-diamond.com/GNU-Linux-Magazine/GLMF-102/8...) explains how to run some of these old Unices, and the author also builds and uses an IRC client on 2.11BSD. It's written in French, but Google translate does an OK job on it.
Look at http://www.tuhs.org/Archive/Distributions/Boot_Images/ for software (you have to look around in the readmes a little). Debian and Ubuntu both have SIMH packages.
Edit: This article (https://connect.ed-diamond.com/GNU-Linux-Magazine/GLMF-102/8...) explains how to run some of these old Unices, and the author also builds and uses an IRC client on 2.11BSD. It's written in French, but Google translate does an OK job on it.