[loxias]

Yes, that's what I said. (although in a comment below this one. ;))

A container is much lighter weight than a VM, yes. (and so is a chroot)

But the MacOS userspace isn't running on the linux kernel, it's running on darwin. So, macos-in-docker would be an entire qemu installation in docker, with a macos image inside that.

EDIT: Ahhh, because it doesn't make sense to run a full operating system in a container, only a single program, I'm guessing that what OP really wants is some way to dockerize a specific (or several) macos apps. To do so, you'd need a way to wrap the linux kernel do it can provide a darwin like api, as well as the same for any required libraries.

OP: You may find this project interesting: https://www.darlinghq.org/project-status/

They made a MacOS to Linux translation (not virtualization) layer of sufficient quality that you an run a decent amount of (text only) native binaries.