Did you configure the Surface Duo Game Area Mode in the settings?

Please test https://github.com/Fate-Grand-Automata/FGA/suites/7968417259/artifacts/340680930

Use Duo mode with Custom offsets set to 0 on all sides.

Surface Duo 1 should still work with left and right set to 192, btw.

Another try: https://github.com/Fate-Grand-Automata/FGA/suites/7984284131/artifacts/341765642

Before, I thought that width was reported as half, that's why I doubled it.

Now, width seems to be the normal value, so FGA treats it as too wide.

To avoid giving you more experimental apps, can you please run

adb shell
dumpsys window windows | toybox sed -n '/Window .*mathewsachin.*:/,/Window .*:/p'| grep -o 'mAppBounds=.*)'

There should be 2 lines of output. Please post them here. They should look like this:

mAppBounds=Rect(0, 103 - 1080, 2268) mMaxBounds=Rect(0, 0 - 1080, 2400)
mAppBounds=Rect(0, 103 - 1080, 2268) mMaxBounds=Rect(0, 0 - 1080, 2400)

Here is the output:

mAppBounds=Rect(0, 0 - 1344, 1832) mMaxBounds=Rect(0, 0 - 1344, 1892)
mAppBounds=Rect(1410, 0 - 2754, 1832) mMaxBounds=Rect(1410, 0 - 2754, 1892)

It pretty much states that one of the FGA windows is covering the left screen and one is covering the right screen. Both are 1892 pixels high.

One of the windows is the app, the other one is the overlay. Since the play button is on the right side of your screenshots, I assume you can't move it to the left side.

I think I have to install the Surface Duo emulator and test it myself, if possible.