While DOS with Windows 286 worked okay, OS/2 for Mach20 never would get past installation.
I finally told my boss that I was getting nowhere with OS/2. She contacted her boss and later relayed to me that OS/2 for Mach20 had been marked as a "non functional product" and would be going away.
The happy ending was that I kept the Mach20 board in my ancient PC and used it for my remaining programming classes. It ran Turbo Pascal and QuickC for DOS quite well.