I've been following this thread since early April but this is my first post as I haven't felt that I had anything helpful to offer. Frankly I still don't but I wanted to share my experience and the path forward (hopefully) that I am going to try. I've been a Mac user since 1986 (with a brief break during the bad years post OS 7 until OS X and the switch to Intel). I've worked in IT in various capacities over the years (mostly help desk and sysadmin stuff) and I regularly use Mac, Linux, and Windows but I much prefer to live in the Mac world when possible. That said, the Catalina disaster that has beset us all has made me question that.
My affected machine is a late 2012 iMac with all the original apple ingredients--I haven't modified anything. I don't have external monitors on it and I do not have VM software installed. While this machine is getting old, it's always been rock-solid since day one. I ran Mojave on it until the end of December 2019 and never had a problem and typically only restarted the computer every couple months or so. Then at the end of 2012, I decided to upgrade to the new OS since it had been out a while. Typically, upgrading the OS with Apple has always been a good improvement: more stability, more features, quicker responsiveness... I've always been amazed how a new OS on apple always seems to make an older machine feel better as opposed to how those upgrades usually go in the Windows world. Initially, the Catalina upgrade seemed to be just that.
After a few months passed (mid-March), I deleted my bootable backup of my Mojave machine because my computer had run flawlessly in Catalina the whole time. Then on March 28, 2020 Apple pushed an update that effectively killed my computer. After that upgrade I would have constant kernel panics always due to the watchdogd counter hitting 0 without a checkin from the windows server. Sometimes my computer would have 10-20 kernel panics between pressing the power button and reaching the log-in screen. If I left it on all day, it would typically reboot 30-50 times a day! There was no way to even use the machine. Again, this was not caused by non-apple memory (it's all factory installed), or external monitors (I have none), or virtualization software (I'm not using it). Nor is it caused by any defective hardware--I've tested everything and it all checks out. Also, I should add, if I boot the computer into Linux it is completely stable and works great. In fact, that how I used my computer from March 28 until late June due to personal time constraints that prohibited me form working on the machine. This problem, it seems to me, is caused solely by Apple's negligence in their code. Problem is, as we all know, identifying the source of the problem from our end seems to be impossible.
So, since June, I gave up on Apple ever issuing a fix--they don't even seem willing to admit they created a problem. I wiped my computer and did a clean install of Mojave. It is stable for the most part but not at all as it was pre-Catalina. It runs okay about 70% of the time but often becomes completely unresponsive for a while requiring me to wait or even walk away until it comes back to life. It never kernel panics though so the endless reboot loops are gone which is at least a small, though somewhat pyrrhic, victory. The fact that this instability has carried back to Mojave even though I did a clean install leads me to believe that they altered code in the EFI that has caused this problem. That also would explain why none of us can find an actual cause let alone solution.
Sorry this was so long. The length is reflective of my level of frustration with Apple. Remember when we all thought Vista was the worst OS upgrade ever? Vista is dead. Long live Catalina, destroyer of Macs!
[Edited by Moderator]
