Just stumbled into this and passing along.
https://www.theregister.com/2017/05/19/new_version_of_os_2_arca_os_5/
Qt 3.x and Zinc used to be big on OS/2.
https://www.arcanoae.com/arcaos/
I haven't dug in to see how current the C++ compiler is nor did I dig in to see if CopperSpice could be built 32-bit. I was a rather ardent OS/2 user back in the day and am impressed at how it refuses to die. Banks and ATMs simply don't trust anything else.