> How can Docker run on FreeBSD when FreeBSD has no cgroups? I think you misread/misinterpreted your reference.
FreeBSD can run 64 bit and 32 bit Linux binaries via it's Linux emulator[1]. Plus FreeBSD has had containers since FreeBSD 4 which was released in March of 2000, except containers on FreeBSD are called jails.
> If MacOS doesn't have certain linux kernel features, neither does FreeBSD.
Just because one operating system doesn't have a feature that does not mean a different operating system does not have that feature.