Now to install the beta or alternative version of the Mac operating system on your external drive. Open a finder window, go to Applications and find the Catalina or Big Sur installer (or whichever. To install macOS Mojave or Catalina you can choose to doing a clean install or doing a direct upgrade. In my case I am doing direct upgrade. For doing direct, either you can install the OS directly from the macOS Installer.App or from the USB.

Hello! It looks like the device is possibly an SSD replacement candidate. I'll have to check into that. I did erase the drive after clicking on the option to view all devices. I deleted both the partition and the root physical drive using the Disk Utility. I'm wondering if maybe the EFI is corrupted or if the creation of the boot records when installing are somehow not what they should be. Other solutions have talked about having to have the Apple support team do a firmware upgrade, fix the EFI, etc., which I'm not sure why I couldn't do myself.

I appreciate the response and will keep working on it while our Apple stores are closed. Thanks!

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May 13, 2020 2:09 PM