I want to make a launch daemon that automatically launches yalu on boot, but I cannot find the app executable. Does anybody know where iOS 10 stores apps?
Long story short is that, unfortunately, only signed code can be ran before the jailbreak and your daemon will fail to launch. If unsigned daemons worked before the jailbreak, they could have already used that as an untether.
In fact, some jailbreak developers discussed this publicly just a few days after this answer was made and they arrived at the same conclusion. They went into it further and and came to the realization that even if they signed it themselves through the Apple developer signing tool, it would not work because only binaries signed by Apple can be executed as a daemon.
Applications have been moved in iOS 10. They're now in
See Andrew's answer for why you can't do what you're asking though.