The earliest stuff was on SunOS/Solaris, which might be difficult to get running today without vintage hardware.
Nokia IPSO (of particular interest to me) was never really VM friendly, even though it was on x86 hardware.
That said, I did see FireWall-1 3.0 in a Windows NT VM a while back, which might be as far back as we can reliably go 🙂
At one point I did have the R55 Policy Editor (what it used to be called before SmartDashboard) loaded on one of my Windows 10 PCs, which I used in Demo Mode.
Which, now that I think about it, might be the best way to demo the older versions: load the old UIs and run them in Demo Mode.
Pretty sure even the Policy Editor from 3.0 supported the Demo Mode (using *local as the hostname).