To reinstall macOS on your Mac Mini 2018 when Web Recovery fails and USB boot is not permitted, follow these steps: Recover from a Time Machine backup: Connect your Time Machine drive to the Mac Mini. If you have multiple backups available, select the most recent one. Click “Restore” and follow the prompts. Use an external bootable macOS installer: Create a bootable macOS installer on an external drive using another Mac with Internet access. Then, insert the external drive into the Mac Mini, restart it, hold down ‘R’, and release when you see the Apple logo.

Should I reinstall macOS Catalina on my Mac Mini (2018 model)? SSD was worn out.

Trial 1: Web Restoration (Alt + Shift + Cmd + R or Alt + R)

All appears good till:

Working Apple Diagnostic tools lead to:

Regardless of how many attempts I make, repeatedly rebooting and retrying the setup always leads to:

Trial 2: USB key

From another Mac, I downloaded Catalina and created a bootable USB installer.

softwareupdate -d --fetch-full-installer --full-installer-version 10.15.6 && sudo /Applications/Install\ macOS\ Catalina.app/Contents/SharedSupport/installer scripts/createinstallmedia --volume /Volumes/UNTITLED 

Despite initial efforts to restart via USB drive.

By subtly tweaking the parameters of our experiment, can we successfully manipulate the outcome and achieve the desired result?

Trial 3: dd

I repeatedly attempted to transfer the USB setup key to the solid-state drive (SSD) via the terminal, anticipating a successful boot-up sequence. Unfortunately, despite my efforts, the device chose to bypass the SSD and instead initiated a reboot into the Web Restore mode.

Stranded in an endless cycle of Apple’s limitations, I’m stuck between a rock and a hard drive: unable to boot from a USB device without an administrator account, which I can’t establish since the disk is blank, and similarly, I’m blocked from creating an admin account because I need to install macOS from a USB key, but that requires an existing admin account.

Thanks upfront for any suggestion.

P.S.: Due to its soldered design, the SSD cannot be easily swapped or upgraded in this particular laptop model.