In this video I will show you how to install the latest Mac OS Sonoma on a 2012 iMac
Step one Download OCLP for Mac
https://dortania.github.io/OpenCore-Legacy-Patcher/
Follow along with this video to finish the install.

***USE CAUTION***
Honestly Sonoma runs like crap on this particular machine iMac 2012, your results may vary but Sonoma really pushes the limits of your graphics card, this 2012 on has a 512Mb graphics card and it idles at about 75% capacity at all times and Target display mode does not work.

I also installed it on my 2013 iMac and it did fare a little better but it has a 4GB graphics card and Sonoma was running a fair amount of it at all times.

Big Thanks to @mrmacintosh and OCLP Team!!
https://www.youtube.com/@Mr.Macintosh

Create Mac OS Sonoma bootable USB

How to download Mac OS Sonoma