I can't upload my skin to Bedrock Edition on mobile, because of messed up granting access to files in Android 12 and newer. It says that the skin image is incorrect, but I double checked if it is 64x64 and .png and it is... As of this changes in Android 12+ is impossible to access game files (/Android/data/com.mojang.minecraftpe) through external file explorers (so game itself cant save the skin and because of it this happens I assume), and in default Android one is possible only view them, not edit, move, copy or anything like that. Before it was possible to get around it by uninstalling updates of default files application but this is not possible anymore. In my opinion, the only one who can fix it is you or the Android developers, but I doubt that anyone who thought of adding such a change will want to change it back.

Hope you'll do something about it and it will be again possible to mess around with addons and skins on mobile, thank you