How to change app icon in Substack mobile app?

curious sub Stack mobile app and to change icon you just tap on your profile tap in the bottom right tap on your icon in top right and tap on app icon and then here you can choose the custom sub stack icon so there are standard ones and there is a night vision so if you like dark theme probably you can select night vision so they only have like two app icons then of course if you there are so many apps like uh Widget icon apps like theme pack or vegetable all of these apps which you can download and then you can replace icons from these apps but probably you will need to be a paid customer there