Comment by OCTAGRAM

DOS emulation is available more widely than Win32 emulation, and there is HX DOS Extender. I would try sticking to Win32 dlls runnable in HX DOS Extender. rundll32 or some other exe host. HX DOS Extender has no paging support and has problem loading multiple exe having no relocation info to the very same 4Mb base address they all usually pretend. DLL should have relocation.

I thought "but what is the problem to generate EXE with relocation?" and tried GCC GNAT (from 2017), and GCC said no. EXE and DLL formats are very much the same, but GCC is completely unable to generate relocatable EXE. A very suprising discovery. More recent toolkits became aware that adding relocation to EXE is not a rocket science, just do the same like in DLL. But these recent toolkits may call APIs that HX DOS Extender does not support yet.