Have a patch request for Optiplex 5260 everything works on this basically out of the box w/ your efi for coffeelake added a couple kexts and its 100% definitely a viable option as iMac replacement consideration for anyone looking for that type of setup. This is the i5 proc I am posting the dump for; I also have the i3 I can post a dump for. i will DM you with the EFI folders for both i5 and i3 optiplex 5260s as well.
https://drive.google.com/file/d/12RxgJJEvNgw8-OlpmQB7eH4Yz0yV5Ie_/view?usp=sharing
