First of all, thanks for all the info. Some interest food for thought here.
*but* only has 1 PS/2 port ...
That should not be a problem: there are ps/2 splitter cables for this. In fact mouse and keyboard are connected to different pins on the ps/2 connector.
I was not aware that those kind of splitters existed. May have to give that a try.
You didn't mention video output ports. I ask because all my units are using HDMI either direct or via a DVI to HDMI adapter.
My setup is a 4 port Tcnewcl 4k KVM switch which takes USB 2.0 keyboard and trackball as well as my 28inch 1920x1200 HDMI monitor. The main computer has a MSI A320M Pro-VD Plus motherboard, another possibility is the ASRock AB350M Pro4 - it has 2 PS/2 ports which you want.
BTW I think you should be thinking about upgrading your KVM switch to enable you to have a much wider choice of motherboards.
Well, that present a bigger issue. I currently have 7 systems running into my KVM. I moved from a set of Linked 4 Port OMNI's I switched to a 16 Port TrendNet TK-1601A about 6 years ago. I tried several that had USB instead of PS/2 ports, but could not get all my systems, (Mix of Windows 7, Windows XP, OS/2 and ArcaNoae) all working with the USB Version, so I went back to the PS/2 port one. Converting all the systems is not a task I'm willing to undertake. I've had good luck going from USB to PS/2 with adapters, but less luck going the other way.
You didn't mention video output ports. I ask because all my units are using HDMI either direct or via a DVI to HDMI adapter.
My setup is a 4 port Tcnewcl 4k KVM switch which takes USB 2.0 keyboard and trackball as well as my 28inch 1920x1200 HDMI monitor. The main computer has a MSI A320M Pro-VD Plus motherboard, another possibility is the ASRock AB350M Pro4 - it has 2 PS/2 ports which you want.
BTW I think you should be thinking about upgrading your KVM switch to enable you to have a much wider choice of motherboards.
Video is not an issue. I've got a mixture of DVI, VGA and HDMI outputs on my systems, I just use the appropriate adapter to convert to the VGA that my switch uses.
The vast majority of OS/2 users are on commercial computers, not home-made from motherboards.
Any Lenovo M series desktop computer in the last 15 years would work with your requirements -- I've tried pretty much all of them.
You can go with the hobbyist market -- It's more of a hobby than a rational decision. I know several skilled hobbyists inhabit OS/2 World. If building your own computer brings joy, go for it.
You can buy refurbished computers from the many of the major electronics retail websites now.
I have not bought a commercial desktop computer in over 25 years. I've always built them from the pieces. That way I don't get any of those nasty windows kludges that the various vendors have put into there systems over the years.