Incomplete system

@leroydouglas answer put me on the right path. I followed the instructions here and was able to successfully install Catalina from the Internet recovery option.

Verify you have reformatted the parent drive and not a volume.

From Internet Recovery (option command R) >Disk Utility>View>Show All Devices

reformat the parent drive as GUID/apfs

Recovery: https://support.apple.com/en-us/HT204904

Hi

in recovery mode you should have erased the volumes, not the system 2GB partition. the ones at the top.

It may not have erased correctly so the volume exists and you cant re install on it.

I have just sorted mine. I have the system partition (the bottom one of the choices) and had 2 choices at the top (volumes)

you need to go into the one at the top and choose 'erase' again until it says its completed successfully. you may have to do this with internet recovery mode.

the parent drive cant be reformatted because it holds the recovery disk image that were starting up from...

Mac HD cant be erased because it has a process that is in use; a kext of some description

computer wont restart anymore either, luckily this one still has a plug that can be pulled.

After that it wont startup unless cmd-r is held. Then the reinstall can begin

happy christmas Tim

It turns out Internet recovery mode is the critical bit.

Otherwise volumes/disks may not be erased properly.

as long as there is still a recovery boot volume command-r will start that one in stead of internet recovery. And you can’t erase the volume you started from.

so it may take some persistence deleting and restarting.

I am having the same issue. Just want to confirm that the data (excel, word files, etc.) have been permanently erased by the time you reach this point and get that error message about the Target Volume. Thanks