Okay, after a bit of time researching online, going through settings on the phone and even trying out an app that falsely states it had immersion mode, even shows it in the free version then suddenly is gone once you make the purchase, but fortunately Google refunded me, as I only spent less than an hour with the app.
What I discovered the problem to be: Running Dex Mode through the PC results in double cursor. I did not check this for other apps yet. I will later out of curiosity if it’s something global. However, I ran the phone through the usb-c port adapter in mirror mode, and it works fine. So, then I thought to run the same set up, and btw, this is phone to usb-c port directly to hdmi, not through the a computer. But when I ran Dex Mode straight to the monitor, I was able to scroll the wheel to a single cursor.
So essentially, running the phone to the computer to the screen running Dex Mode, will cause the double cursor effect.
This is great news, not only for Magic DosBox, but I also use Linux on my phone as well, and also was having cursor issues, but not as bad.