Drying fatty meat in food dehydrator - is it okay for short time consumption?
Yes. It may be fine for immediate consumption.

The problem is the air flow from the drying itself can also accelerate the oxidation of the fat.

When I have dried fatty meat the fat already tasted a bit off.

This is a matter of quality, not safety. If the fat isn't objectionable to you after drying then it is fine. As you said, you should expect the fat to go off and eat it soon.