All appliances have leakage. Leakage that should be so low
as to not add up to a problem. It is doubtful that laptop is
leaking milliamps on startup. IOW there would be something
else on the circuit leaking so much that just a little laptop
leakage could trip the GFCI.

Unlikely that you will find leakage with the ohm meter.
Try. But eliminating other items from the circuit, then
powering on the laptop will probably provide better
information.

Informative may be a current measurement of that circuit's
ground wire. How much current (in AC milliamps and DC
milliamps) is flowing down that ground wire for various
powered on appliances on that circuit?

johnhh wrote:
I'll run the resistance test when I get back to the boat, but I
don't see that it is going to tell me anything since the leakage
only occurs when a load is first applied to the DC side of the
power brick. Even at that, it takes more than just applying a
load since there is a load charging the batteries even if the
laptop is not turned on. I haven't been back to the boat since
I started this thread, but will get more info the next time I
go up.