Some posts showing FOG is capable of using these particular machines, but the users are using new versions (beyond 1.2.0) of FOG.
https://forums.fogproject.org/topic/8902/dell-optiplex-5040-m-2-256gb-pcie-nvme-class-40-solid-state-drive
https://forums.fogproject.org/topic/6686/can-t-register-optiplex-5040-tsc-fast-tsc-calibration-failed
https://forums.fogproject.org/topic/7443/0-10-6-client-breaking-sysprep
https://forums.fogproject.org/topic/7759/pxe-chaining-fails-on-ssd/7
https://forums.fogproject.org/topic/9587/blinking-cursor-after-booting-from-hard-drive-in-fog-menu-on-optiplex-5040s