Cannot update - you may not install to this volume because the computer is missing a firmware parti

[yalag]

When I try to update my external drive from high sierra to mojave, it doesnt let me. Give me this error

'you may not install to this volume because the computer is missing a firmware partition"

How to fix?

 

[haralds]

Install High Sierra again. This should restore the required partition for the firmware update needed to boot APFS.

You can search for some of the other posting on what happened with this update.