actually I don't have had a Broadwell / Skylake which I can play with.
I have a MacBook Pro 2013 Late (Haswell). But I wouldn't try out something on my production laptop anyway ;)
I also have a two Xeon Sandy Bridges lying around, but I didn't tried em, but I guess even with some changes it would run on it. I just didn't had time, after it compiled it already was 2 o Clock at night.
It will likely boot on earlier Intel platforms, though some tinkering may be necessary. The focus has been on Qemu and on some modern UEFI based systems (and the latter booting with gigaboot20x6, also part of the Fuchsia repos). Debugging early boot / bringup issues is massively easier if the machine has a standard serial port.
I also have a two Xeon Sandy Bridges lying around, but I didn't tried em, but I guess even with some changes it would run on it. I just didn't had time, after it compiled it already was 2 o Clock at night.