+[UIViewController attemptRotationToDeviceOrientation] does what it says on the tin: attempt to rotate to the device's orientation. It does, however, not rotate the view controller to match -[UIViewController supportedInterfaceOrientation] when the current device orientation is not supported by the view controller it polls. I whipped together th…

UIViewControllerAttemptRotationToDeviceOrientationWorkaround.m

UIDeviceOrientation actualDeviceOrientation = [[UIDevice currentDevice] orientation];
BOOL changedDeviceOrientation = NO;
		
if ((self.supportedInterfaceOrientations & (UIInterfaceOrientationMaskLandscapeLeft|UIInterfaceOrientationMaskLandscapeRight)) == 0)
{
	if (UIScreen.mainScreen.bounds.size.width > UIScreen.mainScreen.bounds.size.height) // Device is in landscape orientation
	{
		[[UIDevice currentDevice] setValue:@(UIDeviceOrientationPortrait) forKey:@"orientation"];
		changedDeviceOrientation = YES;
	}
}

[UIViewController attemptRotationToDeviceOrientation];
		
if (changedDeviceOrientation)
{
	[[UIDevice currentDevice] setValue:@(actualDeviceOrientation) forKey:@"orientation"];
}