How to completely remove android from H9SE TWIN

Unless its causing you major issues. I would be very careful about doing so.
You would need to reflash your box with a compatible recovery image using hitools and a special cable.
If you do it wrong or flash the wrong alternative image, then you can completely brick your entire box.

I did this with my dinobot 4k and turned it into an Anadol Eco 4k. But only because I had no choice.
But that was doing lots of research and experiments to eventually find a compatible recovery image and to get it working.

If you want to read by Dinobot journey to bring it back from the dead. my post is here. The process of what I did is explained in the post.
I killed my dinobot