Do you need to UL Certified the enclosure with the board inside?
The Raspberry PI is not UL approved, to the best of my knowledge.

The original intent was not to have any certification done at all since it's essentially a development kit. However, things changed and they were forced to do some EMI and ESD tests to get CE certification , which they successfully did.

They're OK for CE, FCC and C-tick approvals, but not UL. Don't be surprised if UL doesn't want to do a full investigation, including the Pi. You'll likely also have to guarantee that your setup will use an approved power supply for the Pi.