Updated last week and same is happening for me (iMac 5K 2017). I got rid of my iPhone for this same reason, and hate that it's a pain to go back (if not almost impossible) to previous OS, when all I need is my devices to continue working as they were before, I mean like a day before updating. I already managed to get my hands on an NVIDIA GPU to say goodbye for good to Apple. I haven't got an exciting update in the last decade, all the oposite.