Thank you for the details, that helps us understand the situation.
The core concept of Buns and Poops is seamless blending into the desktop through background transparency. Our current revenue does not allow us to ensure that experience across the wide variety of Linux environments, which is why we have not been able to commit to Linux support.
As a side note, the transparent square near your cursor is intended behavior, it is required on Windows to allow mouse input to pass through the app.