This is more an android R tip, but useful nonetheless! If you go to settings, about phone, software, tap Android R a bunch till the green screen pops up. Rotate the dial till you see the 😺 at the bottom and it says android 11 (Might have to try a few times).
Then the Cat game is active! Set out treats and start collecting Cats!
Extra Tip, Normally there is a toggle in the quick settings, but I couldn't find it. So I just set a Nova (Launcher) activity to set out the treats I choose.