Upgrade stalled from Mojave to Catalina on Late 2015 iMac
It has been 18 hours. iMac has been stalled on black screen with Apple saying "estimated time remaining" for 17 hours or more. I've seen some comments that say it took as long as 24 hours but finally finished. Is there any new information on this problem? Is there a way to cancel the update and go back to Mojave?
iMac 24″, macOS 15.3