Gamescope does not support OpenTabletDriver (user mode tablet driver)
I am not sure if this is an issue of Gamescope or OTD, but I am going to assume it is Gamescope. Essentially, the compositor seems to be blocking OTD from moving the cursor in some way as the cursor doesn't seem to move at all and just hangs out in the bottom right when you try to use your pen while OTD is open.
I am going to assume this is most likely due to the fact that it is a user-mode driver? I have no knowledge on compositors to be able to say for certain.
The project is available here if you would like to see it for yourself: https://github.com/OpenTabletDriver/OpenTabletDriver
Forgot to mention that this is present on both X11 and Wayland.
It happened to me as well.My cursor is fixed at the top left.it's running on X11.
Still an issue.