We have minimum deployments set to iOS 15 in one of the app for both application and widget target.
When install app in simulator or real device using Xcode 15.4, it works fine in iOS15, iOS16, iOS17 and iOS18 beta.
When install app in simulator or real device, using Xcode 16 beta 6, it works fine in iOS16, iOS17 and iOS18 beta but in iOS 15, our app doesn't show in widget gallery.
Xcode 16 introduced a new setting, Enable Debug Dylib Support
While this is being investigated, try setting ENABLE_DEBUG_DYLIB=NO in your widget executable target as a workaround. The crash you're describing looks related to a new executable bundle layout for debug build products in Xcode 16.
Note that this should not affect your customers at all since release builds are not laid out this way. It only affects debug builds.