Salty, Mine just has Intel HD, did not know Surface Pro could have two display adapters.
My Inspiron XPS has an old Geforce Nvidia 2nd display and they have display software
called physics that allows you to chose which display to use by program etc. which works fine with OpenCPN
and was very useful because the onboard Intel HD Display 3000 was slower and did not have fully developed opengl.
I am glad you got that figured out and reported it, as that helps everyone. I never would have considered it as a possibility.