Word on the street is that as long as you really don’t use push notifications this will not cause your app to get rejected. So you can safely (?) ignore this warning and continue to submit your app.
This issue was described on GitHub here, and a solution is being discussed here. It’s apparently somehow related to Flutter using the UIApplicationDelegate callback:
- (void)application:(UIApplication*)application
didReceiveRemoteNotification:(NSDictionary*)userInfo
fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler;
I’ll let someone else explain the exact reason more clearly. Keep an eye on the GitHub issue.
For now I am just going to ignore the warning.
Update: I submitted my app, it was accepted, and there hasn’t been any problem with it since then. So just ignore the warning.