TL;DR: Use Apple Configurator to downgrade a 2018 Mac Mini to macOS Mojave—don’t use USB installation.

I run automated 32-bit apps on macOS using an older Mac Mini. Since macOS Mojave was the last version to support 32-bit apps, anything newer breaks my workflow.

The last Mac Mini model that can technically run 32-bit apps is the 2018 Intel Mac Mini. I found a high-spec unit on sale—at under 15% of the original price. With a 6-core Intel i7, 32GB RAM, 1TB SSD, and 10Gbps Ethernet, it’s a serious upgrade. It arrived running macOS Sonoma.

To get my 32-bit apps working, I attempted a USB installation of Install macOS Mojave from the App Store. That seemed promising… until I hit problems:

  • The Mojave installer would boot, but Recovery Mode wouldn’t.
  • I got cryptic errors like -1000F during boot to recovery.
  • The T2 chip blocked older 32-bit apps due to its security settings.
  • But those settings couldn’t be changed—because Recovery didn’t work.

Total Catch-22.

Solution: Use Apple Configurator (from the App Store) on another Mac. Then:

    1. Connect the two Macs with a stock Apple USB-C to USB-C white cable (the one from a charger).
    1. Use the Restore function in Configurator to wipe and reflash the 2018 Mac Mini.
    1. After the restore, boot into Recovery and install macOS Mojave.
    1. Now Recovery works, T2 settings can be adjusted, and 32-bit apps run.

Sharing this in case it saves someone else the headache.