Go to the Dragonframe website, click on Support, then on Camera Support. Under "choosing the right camera" there is a link to show which cameras are supported. Under Sony Alpha, the 3rd maker down the list, all the supported models are listed. I clicked on the A6400. It looks like it works, here are the setup details: https://www.dragonframe.com/camera-setup/sony_alpha_a6400/
It says the Sony A6400 will work with Dragonframe 4.2.2, but not with 3.7.3 or older.