In-A-NutShell 13.2.0

available on themezer https://themezer.net/packs/In-A-Nutshell-397
the icon ratio is 2:3 and fully supports https://github.com/Slluxx/IconGrabber (made by sluxx)

but you can also use NX-GIC icons to mass transfer icons as a temporary measure https://github.com/sodasoba1/NSW-Custom-Game-Icons/wiki

sys-tweak guidance: https://gbatemp.net/threads/custom-game-icons-tutorial-and-sharing-hub.574675/

sys-tweak (tested on 13.2.0|AMS 1.2.6|S) : https://gbatemp.net/threads/custom-game-icons-tutorial-and-sharing-hub.574675/post-9738297