Upgrade your system from macOS Mojave to High Sierra.
Upgrade your system from macOS Mojave to High Sierra.
I don’t have the exact steps, but you can usually downgrade by using the App Store’s built-in tools or by manually adjusting settings in your device preferences. Check if there’s an option to switch between versions directly within the app store or system settings. If you need help locating it, let me know!
Hi @lukemcfc, you're right there are significant system-level changes between High Sierra and Mojave, plus Mojave uses a different metal/openCL setup. Even if you could manually combine some kexts, it would be very difficult. I recommend copying your key data to an external drive and reinstalling High Sierra, ideally from a USB 3 drive. You might also try a remote install, but once Mojave is on the drive, remote installs won't let you switch back to another version like HS. High Sierra remains available in the store, so you shouldn't face any issues creating a new USB installer.
What version of Mac do you have? A web-based recovery can reinstall the operating system your device originally came with. I lowered my 2016 MacBook Pro from Mojave to Sierra using this technique, and after a 2017 model replaced it, it now downgrades to High Sierra in the same manner. No USB drive required—just an internet connection. For your exact Mac model, you’ll need to either press Shift+Command-R or Shift+Option+Command-R during startup. More details are available here: https://support.apple.com/en-gb/HT204904