Is the linux kernel and gnu userland a bastion of security? Of course not, but it is still magnitude orders better than M$ counterparts for a multitude of reasons. Not even M$ runs windows as a baseplate on Azure. It is a net positive for humanity if more people and orgs ran linux based operating systems.

On BSD you use FIBs to declare process specific routing tables, on Linux you use firewall marks to do the same, then just route all trafik through the vpn uplink and deny any other.

jfs+lvm on personal machines, ceph on storage, I used to use zfs on solaris and freebsd but haven’t touched it in linux (there isn’t any good reason, and I prefer to not break licensing)