Early 2008 iMac that I erased prior to giving away.
However I need to install El Capitan which comes as a dmg with imbedded ap file. How do I do this? And if you say clone drive how do I do that?
iMac 24″, 12.5
Question marked as
In order to create a bootable macOS 10.11 USB installer you will need access to another Qualifying Mac from 2008 to 2015 so you can run the .pkg file which will extract and create the actual installer and place it into the Applications folder. Here is an article which shows which versions of macOS are compatible with various Apple hardware as my estimation of compatible Qualifying Macs is just a generalization:
https://eshop.macsales.com/guides/Mac_OS_X_Compatibility
Or you can purchase an OSX 10.6 Snow Leopard upgrade DVD.
If the internal drive has not been erased yet, then you can boot into local Recovery Mode using Command + Option + R to access the local recovery mode macOS installer for the currently installed OS.
Another option would be to install Linux Mint to the iMac which would provide an up to date & current non-Apple OS with access to the current versions of popular web browsers (Firefox, Chrome, Vivaldi, etc.) as well as lots of free open source apps such as LibreOffice. Linux also has access to Zoom & Teams. In my opinion this is the best option unless someone has a need to only run an older version of macOS or a specific version of an old app on macOS.