After putting off the process for a few days, I successfully completed the system update to macOS Sequoia 15.4.1 this morning on an unsupported 2017 iMac.

Before proceeding with the upgrade, I updated to the latest version of the OpenCore-Legacy-Patcher (OCLP) version 2.3.2 (at the time of writing) and rebooted the iMac to make sure everything was in working order.

Once I successfully booted into the iMac, I followed the following procedure.

  • Download macOS Sequoia 15.4.1 from System Settings > General > Software Update.
  • Reboot the system when prompted.
  • Wait for the update to finish (around 20-30 minutes).
  • Login to macOS.
  • WiFi will be broken; this is normal as the OCLP patches are removed every system update.
  • OCLP will now prompt to re-install the latest root patches. Agree, and follow the steps on-screen.
  • Reboot with Option key held down.
  • Select “EFI Boot” initially and then your Macintosh HD boot drive in the second step, after proceeding past EFI Boot.
  • Login to macOS.
  • Everything is working again, including WiFi.

There is still one more important step. You don’t want auto-update enabled on an unsupported system as there are circumstances that can cause your system to become unbootable when you attempt a future update. So turn off auto-updates:

  • System Settings > General > Software Update >
  • Tap the circled i beside towards the right of the Automatic Updates panel.
  • Ensure the following are disabled/not toggled on:
  1. Download new updates when available
  2. Install macOS updates
  • Tap “Done”

That’s all folks!

Important: this is not intended as a how-to guide. This is just me explaining what I did to update my system. Choose to follow along at your own risk.

✏️