Is Microwaving considered dry heat or moist heat and why? I am wondering if microwaving food is considered dry heat or moist heat.

It has a similarity to frying in oil as it doesn't heat it in water. And I know frying in oil is dry heat.

But if I put bread in the microwave it goes soggy, not brown (no Maillard reaction), so that suggests it's moist heat.  I understand the reason it doesn't brown is because the food surface temperature is low, unless a "browning pan" is used in the microwave.

Are the terms dry heat vs. moist heat dependent on whether the surface temperature of the food is such that browning occurs? Or is it based on whether or not there is water/steam surrounding the food?
It is not inherently either, but most often it performs similarly to moist heat.

Microwaves work by directly exciting polar molecules within the food, usually water or fats.

If the food contains significant quantities of water (like most fruits, vegetables, meats and so on) then microwaving usually acts very much akin to steaming, which is a moist heat method.

In some fringe cases, most particularly bacon, where there is a significant amount of fat that can be directly excited to temperatures higher than water can obtain without evaporating, you can essentially fry by microwave... and of course, frying is a dry heat method.