I know this is an older thread, but I just installed ScummVM on my tablet recently and ran into the exact same problem and Google led me here.
I'm not an Android developer, but I took a look at the code and I think I found the bug in the Android backend MouseHelper. It looks like the check to see if the event came from a stylus
here has a problem. According to the Android
InputDevice docmentation, the SOURCE_STYLUS "merely indicates that an input device is capable of obtaining input from a stylus."
It appears the fix to check for stylus input is to instead check the tool type returned by MotionEvent#getToolType(int). I wrote a small test app and confirmed that for touch events the Fire HD8 (2020) tablet has the InputDevice flag for SOURCE_STYLUS always set. I also confirmed that checking the ToolType of a touch screen event returned TOOL_TYPE_FINGER and not TOOL_TYPE_STYLUS. I don't think this is specific to Fire tablets; I was able to reproduce it on an emulated device, but I don't have any other real tablets.
I added this information to the bug ticket and I will try to setup my machine to compile ScummVM for Android sometime this week to test a fix. If that works, it seems like I would be able to just submit a pull request against that ticket if I read the developer wiki page.