When I received my EM_NFP assignment, I also received a list of recent assignment which I may post here for visibility. The following are therefore official e_machine EM_* assignments.
EM_LANAI 244 Lanai processor
EM_CEVA 245 CEVA Processor Architecture Family
EM_CEVA_X2 246 CEVA X2 Processor Family
EM_BPF 247 Linux BPF – in-kernel virtual machine
EM_GRAPHCORE_IPU 248 Graphcore Intelligent Processing Unit
EM_IMG1 249 Imagination Technologies
EM_NFP 250 Netronome Flow Processor (NFP)