When I was in school I once used a IOS emulator running inside a docker container of MacOS running on a linux machine. It works surprisingly smoothly.
The difference between Docker and a VM is that Docker shares a kernel, but provides isolated processes and filesystems. macOS has a very distinct kernel from Linux (hence why Docker on macOS uses a Linux VM), I would be shocked if it could run on a Linux Docker host. Maybe you were running macOS in a VM?
Nope, Mac OS as a Docker container, it’s a thing: https://hub.docker.com/r/sickcodes/docker-osx
Also you don’t need a Linux VM to run docker containers on a Mac host btw