Cannot create preboot volume for APFS install

I don't know if there is another way. This thread indicates you need to erase the drive. However, that was for High Sierra and the OP surmised it had to do with the existing APFS volume. You would need to erase and format as APFS, but Mac OS Extended should still work as you can upgrade from OS's previous to High Sierra.

Hi Caleb_Chong,

I recently ran into a similar issue, but with the Catalina installer. Try to reproduce the issue, then show the Installer Log (at the top menu bar, select Window, then Installer Log). The Installer Log provides additional details as to the real cause behind the issue, and the relevant errors will usually be stated near the end of the log.

What fixed it for me was ensuring that both the existing Preboot and Recovery volumes are mounted as read-write (instead of read-only). Both of these volumes are hidden by default, so you'll need to use Terminal in order to accomplish this.

Before running the macOS installer, open Terminal and run these commands (in order):

• diskutil mount Preboot
• diskutil mount Recovery
• sudo mount -uw /Volumes/Preboot
• sudo mount -uw /Volumes/Recovery

In the last two commands, if Terminal says sudo: command not found, you're running from the Recovery OS. In that case, remove "sudo" from the last two commands.