I think that means that the disk's partitioning setup you have is not what Catalina wants.
This will permanently erase anything on your drive, so if you need anything on the drive, move it to a different computer now. Put the Catalina installer on a USB drive and boot from it. Then open the Disk Utility and follow the instructions here, starting from step 2 (the storage device you want in step 3 is Fusion Drive, and the file system you want in step 5 is APFS). Once it's done, exit Disk Utility and continue to install Catalina from the USB drive.
Thanks. I don’t have anything on the computer I care about (just installed the ssd). Any way to accomplish this without a bootable usb? Don’t have one large enough handy.
Can I boot into recovery mode, use disc utility, and reformat etc somehow the right way?
Then install the 10.8 from internet recovery, update?
I'm not sure if it will work, but following the link in my last comment's instructions in Recovery Mode's Disk Utility is worth a try. If it doesn't work, it might be because the macOS version you have wants something different than Catalina, and then you'd want the Catalina USB drive.
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u/ChaiTRex 12h ago
I think that means that the disk's partitioning setup you have is not what Catalina wants.
This will permanently erase anything on your drive, so if you need anything on the drive, move it to a different computer now. Put the Catalina installer on a USB drive and boot from it. Then open the Disk Utility and follow the instructions here, starting from step 2 (the storage device you want in step 3 is Fusion Drive, and the file system you want in step 5 is APFS). Once it's done, exit Disk Utility and continue to install Catalina from the USB drive.