Thank you very much @CaseySJ for the detailed instructions and EFI folder. I have created two previous Hackintoshes from older prebuilt business computers and decided I wanted something using current components.
An observation: whilst I was waiting for the Graphics Card to arrive I used the...
Here are direct download links for macOS installers with valid certificates:
Catalina - https://support.apple.com/en-us/HT201475
Mojave - https://support.apple.com/en-us/HT210190
High Sierra - https://support.apple.com/en-us/HT208969
Sierra - https://support.apple.com/en-us/HT208202
Tried this fix but it did not work for me. So I dug a bit deeper and eventually got the Security Update to install.
I deleted a folder from the drive called "macOS Install Data" and ran the updater again and it worked.
Your instructions for the HP were so good I decided to try the Dell 9020 MT and am awaiting arrival of a Gigabyte Radeon 4GB RX 570 GAMING PCI-E VGA Card and modDIY 24-Pin to 8-Pin Adapter Cable to take full advantage of my new setup.
I would like to thank @Sniki and @trs96 and others for the effort they input to support this community.
This is a caution about using 4K monitors with a HP Elite i7-3770 SFF using Intel HD4000 Graphics.
My late 2011 27" iMac would not support Mojave so I purchased this HP Elite 8300 I7-3770...
Security Update 2019-001 10.14.6 is proving difficult to install after many, many restarts it was eventually completed on my Dell Optiplex 9020 but my HP Elite 8300 i7 SFF is not having a bar of it.
The HP Elite 8300 i7 SFF gets 2 restarts then keeps giving this error message:
macOS could not...
I have come across this problem even when installing genuine Macs with a version of macOS. There are 2 steps I take, firstly disconnect the Ethernet and/or WiFi, then do a Get Info on the version of Install macOS xxx and look at the Modified Date. Set the System Date to that date. You can do...