Lvgl has a function to get the last key pressed (lv.indev_t.get_key), through which you can determine the key press (Key Down). Is there any way to determine whether a key is released (Key Up) regardless of the current object?
As this question is not Micropython specific, I think you have a better chance to get responses if you post to the How-To category.
I think the standard way is to register event listeners on objects and not directly access indev.