I've been trying to get the Sirius/XM streaming app on my iPhone 8s Plus to work with ios12 on my AVIC-8000NEX but the app doesn't seem to work. I get no display on the LCD screen or it just freezes or just doesn't do anything and then none of the other apps on CarPlay will work either. Has anybody noticed these issues with the Sirius/XM app or any other CarPlay app with iOS 12 ?

There was an update to the Sirius/XM App on the iPhone for IOS12 today.  You might want to check that out.

I have a radio subscription, so I don' use the App.  All my other apps work perfectly with Carplay on the 8400.