As a technonumpty I took the plunge and did the upgrade to Sequoia on my late 2015 27" iMac, and it's been great with 1 exception, it no longer see's my iPhone 11 so the phone does not charge on the iMac, or appear in music etc. The Apple lightening cable has always been in port 4 without issue, so I've changed cables, tried all 4 ports, and I tried my wifes iPhone 12 and nada. Yet my time machine, and other things pligged into the ports work, and I tried both phones on my M2 MBA also runing Sequoia, and the charge and apper in music etc. So whatever funkiness is going on it's definately an issue on the iMac.
The version of Sequoia was 15.7.7 and the version of OCLP is 2.4.1. So I checked and there was an OS upgrade to 15.7.8, so I did it and it now shows as 15.7.8 in about this mac. OCLP said I needed to upgrade patches, but every time it fails with the message in the photo. So now I'm in big trouble, the icons are on my home screen but the background is black, and I cannot connect to the internet via wifi or bluetooth hotspot.
On the plus side, it see's the phones again, but the mac is just a big typewritter now, so I've created a bigger problem than I started with..... any and all help appreciated to fix this.