Containers are namespaced processes. These processes exec against the corresponding kernel they require. There is no workaround: if you have an ELF binary calling Linux syscalls it can only run on a Linux kernel†, so to run that you need a VM††. It's not as bad as it appears thanks to memory ballooning†††.
Conversely if you want to exec a Windows binary in a container, the Windows kernel needs to provide process namespacing features (which it does). And if you want to exec a Darwin binary in a container, then the Darwin kernel needs to provide process namespacing features (which it doesn't).
† WSL1 was implementing the Linux syscall API on the Windows kernel, which proved to be much more complex than it appears to be.
†† Or colinux (https://en.wikipedia.org/wiki/Cooperative_Linux), or user-mode Linux (https://en.wikipedia.org/wiki/User-mode_Linux).
