There's an user who has made a couple of version of unreal ( around ue4.1-up to ue4.26) work on FreeBSD and even recieved Epic megagrant, has a full on guide on FreeBSD forums and github tutorial on setting it up a native compile of UE on FreeBSD. Potential unofficial channel to help with the cause? Could bring intrest to a full official path
#FreeBSD (Unofficial platform channel)
desert barn