I've tried this ... I've haven't got much mileage on this, sadly.

Many Linux syscalls are unemulated and things like /proc/<pid>/fd/NN etc are not "magic symlinks" like on Linux so execve on them fails (i.e there is rudimentary /proc support, it's not full fleshed out).

TL;DR Linux containers on FreeBSD via the podman + linuxulator feel half baked.

For example, try using the alpine container... `apk upgrade` will fail due to the /proc issue discussed above. Try using the Fedora container `dnf upgrade` will fail due to some seccomp issue.

The future of containers on FreeBSD is FreeBSD OCI containers, not (emulated) Linux containers. As an aside, podman on FreeBSD requires sudo which kinda defeats the concept but hopefully this will be fixed in the future.