So, I'm to the point of trying to migrate things from a pre-2016 MBP to a 2016 MBP. This appears to be dongle mandatory. Old machine has firewire and possibly thunderbolt, which I could use with target disk mode, but new machine has neither. (Also, I have never had migration assistant run successfully using thunderbolt.) I don't have any firewire<->USB-C adapters, and haven't seen any yet. So I can try USB-C to Thunderbolt for target disk mode. Or I can make fresh time machine backups, and use a USB-C to USB-A dongle to attach to a drive. This... seems suboptimal. Am I missing a thing? Was there supposed to be a way to do this that didn't require at least one brand new cable I'll probably not need for anything else? EDIT: So apparently, you can't do the target disk "just hook up the old mac's disk" thing anymore. You have to have a time machine backup, or be running migration assistant on the old mac. Also, apparently, this 4-year-old machine running OS X 10.10.5 has a "newer" iTunes, which means that the iTunes library can't be copied. It can't be copied because it can't be used without newer iTunes, and "okay, copy it, I'll update iTunes once I can boot at all" is not one of our options.