Reporting something positive for a change: at work, I recently retired the last six of our 13-year-old Dell R415 servers, which were replaced with a combination of new Dell R360s and 7-year-old whitebox Supermicro machines. I cloned the old machines onto the new machines' disks, made small configuration tweaks (UEFI, serial console settings, network interface configuration) and after a couple of initial hitches everything Just Worked. #FreeBSD of course.