Open SIMH is a highly portable, multi-system simulator.

SIMH is a framework and family of computer simulators, initiated by Bob Supnik
and continued with contributions (large and small) from many others, with the
primary goal of enabling the preservation of knowledge contained in, and
providing the ability to execute/experience, old/historic software via
simulation of the hardware on which it ran. This goal has been successfully
achieved and has for these years created a diverse community of users and
developers.

See the following link for a list of simulators and documentation:
https://opensimh.org/simulators/