Ok so I mucked around a bit more and supplied 4.8V to VCC_INT directly from the lab supply. The board started consuming about 0.8A and when I hooked it up to the PC, the board got enumerated. I was able to run the LimeQuickTest, and the board passed all the tests.
So that’s good - now I need to find whats wrong with the power source selection circuitry.
P.S. Sorry if this has quickly turned into a monologue thread.