Apple Patches

Lately I’ve been playing with some iMacs, generally trying to upgrade them farther than Apple will generally allow. Officially, the iMacs I’ve been working with are upgradable to High Sierra, but I have upgraded them to Catalina using a patched version of the OS, by someone called Dosdude1. Today, I upgraded an iMac from Late 2013 to Big Sur, using a patched version of the OS.  (Thank you Tom and Jan)

The instructions for going to Catalina are HERE.   Generally for 2008 or newer Macs. The web site has the specifics. It’s a clear and easy to follow process. The main site to read about patching Big Sur is HERE.   Generally for 2012 or newer macs.
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The site where I downloaded the program that creates the patched Big Sur is HERE.    (it’s at the top right. I used “Patched Sur v1.0.1”)

The only problem I had was formatting the USB’s partition table to be GUID. It’s easy, but it didn’t immediately show up in the disk utility. Do this: from the View menu choose "Show All Devices" and then you will be able to see the actual USB device that holds this volume and erase it, selecting the partition type.

I am now running Big Sur on an iMac, Late 2013. The whole installation process, including the downloads and creation of the bootable flash drive, takes several hours. I did not sit and watch it, for the most part. When it seemed like it was going to take a long time, I went and did other things. It did an update to the iMac, not a clean install. I think it requires the existing OS to be either Catalina or Big Sur in order to install.
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 As always, do not mess with your OS unless you have a backup of your data. 

an update: I upgraded my 2012 iMac to Big Sur, without issue. Everything was where I left it. Mind you, I don't have any fancy software installed that could be an issue. I do have VirtualBox on there with Windows 10, and it needed to run an update for it, but it still works. And yes, I did make a backup before installing.