You don't need open-watcom to compile 9x applications from other OSes... both gcc and clang, as well as wine, have multiple options for cross-compilation, no VM or docker needed.
I routinely use all 3 methods for compiling my own 95/98 applications from Linux.
For gcc I use the mingw toolchain, which is available as the mingw-w64 package on Debian-based systems, or https://mxe.cc/.
For clang I use clang-cl with the VC6 SDK. clang-cl pretends to be the Microsoft cl.exe compiler and actually works quite well if you know the right options to give it.
And finally, using wine you can either run the original MSVC toolchain compilers, or versions of gcc that were compiled to run on Windows directly; there are both old and new gcc versions that can produce Win9x binaries if you know where to look.
Some resources that have helped me over the years as well:
https://glizda.wordpress.com/2021/05/19/compiling-programs-for-windows-95-and-pentium-in-2021/