Installing Linux on a 2020 iMac

Complete guide to installing Ubuntu on a 2020 27" iMac and bypassing Apple DEP/MDM enrollment issues.

Why Linux?

If your iMac is enrolled in Apple DEP (Device Enrollment Program) or MDM (Mobile Device Management), updating macOS may force corporate enrollment. Linux bypasses this entirely — once macOS is wiped, the DEP record in Apple's database becomes irrelevant because you'll never run macOS on the machine again.

Hardware Compatibility

Good news: 2020 iMacs have Intel processors (before Apple Silicon), so Linux support is mature.

• Graphics: Intel integrated graphics and AMD GPU are well-supported
• Wi-Fi/Bluetooth: Broadcom chips may need proprietary firmware, but most distros handle this automatically
• Boot: Linux boots via EFI, no issues there

Prerequisites

• USB drive (8GB+)
• Another computer to create bootable USB
• Ubuntu 24.04 LTS ISO: https://ubuntu.com/download/desktop
• Backup everything with Time Machine first

Step 1: Create Bootable USB

Download Etcher (https://etcher.balena.io/), select the Ubuntu ISO, select your USB, and flash it. Safely eject when done.

Step 2: Boot from USB

1. Insert bootable USB into iMac
2. Power on and immediately hold Option (⌥) key
3. Select "EFI Boot" from boot picker
4. Press Enter

Step 3: Install Ubuntu

1. Choose "Install Ubuntu" from GRUB menu
2. Select language and continue
3. Installation Type: Select "Erase disk and install Ubuntu" — this wipes macOS entirely
4. Enable LUKS encryption if desired (recommended)
5. Create your user account
6. Click "Install Now"
7. Remove USB when prompted and reboot

Step 4: First Boot Setup

Your iMac will boot directly into Ubuntu. Run:

sudo apt update
sudo apt upgrade -y

Check for proprietary drivers:

sudo ubuntu-drivers devices
sudo ubuntu-drivers autoinstall

Reboot after installing drivers.

Common Fixes

No Wi-Fi

sudo apt install broadcom-sta-dkms linux-firmware -y
sudo reboot

Brightness keys not working

sudo nano /etc/default/grub

Find GRUB_CMDLINE_LINUX_DEFAULT and add acpi_osi=:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi="

sudo update-grub
sudo reboot

Result

• ✅ macOS completely erased
• ✅ DEP/MDM prompts gone forever
• ✅ Ubuntu 24.04 LTS installed (supported until 2029)
• ✅ Your iMac is a useful Linux desktop again

Guide based on conversation about bypassing Apple DEP by installing Linux on an iMac that can no longer update macOS.