You say you suspect that the camera is MTP, but have you tested it with anything else? It’s worth checking the settings on the camera too, to check what it’s set up to do when it’s connected to something else.
As you’ve said, mass storage devices work with Xiaomi phones, so changing the camera to mass storage mode should work too, and will just mean that you have to browse to the correct folder 👍
I just pulled my back and broke my hips reading this, it made me feel so old 👴🏻