Just changing the root widget of my application from QWidget to QQuickWidget fixed the problem. Well, that was way easier than I expected! Thanks for the help.

Probably a better solution is to select the Qt Image Formats module in MaintenanceTool (the online installer). It isn't installed by default and won't include webp support.

@Christian-Ehrlicher I have used the -appstore-compliant option on the final .app made with Xcode. I used nm on the .app after using macdeployqt and it still showed the presence of the two APIs within it. I think I will have to make my own custom Qt using the appstore-compliant feature. Surely you mean I have to compile Qt with the "appstore-compliant" feature turned ON? I know it is supposed to be turned ON by default for Qt downloaded through the maintenancetool. Maybe the Qt 6.4.2 that's available through the maintenance tool wasn't built with the appstore-compliant feature turned ON?