Trying to set boot-args with nvram gets "general error" on Sierra
The kext signing restriction was integrated into System Integrity Protection starting in El Capitan, and as a result the old disable flag no longer works. But there's a new way to do it: boot in recovery mode, and run the command csrutil enable --without kext. I haven't tested it, but my understanding is that this will turn off the kext requirements, while leaving the rest of SIP enabled. If that doesn't do it, try csrutil disable to turn SIP off entirely.