I see this requirements (not UL specific, just plain IEC 1010)
If the chassis isn't connected to safety ground (through cables with sufficient cross section according to the power supply fuse), the circuit needs reinforced isolation against the chassis metal. Using "metal conduits" or simple isolated wires without an additional isolating jacket won't be acceptable.
Routing PE through PCB is only acceptable if the PE conductor cross section is sufficient for 20 A fuse, e.g. >= 1.5 mm².
Creepage between PE and other mains terminals must not necessarily comply with reinforced isolation, I think, but that's probably a lesser problem.