iMac 27” mid 2011 SSD RAID

After erasing SSD RAID 256(2x128) and formatting to APFS Ventura installer states “You may not install to this volume because it is part of an AppleRAID”.

I upgrade a few years ago by removing CD driver and installing SSD to launch OS and run software while keeping original HD for file storage. Currently running macOS Sierra and attempting to install Ventura.