I have formatted and partitioned T7 APFS GUID Partition Map trying to Make the T7 my Default Boot Drive with IOS Catalina with. After several attempts resulting in a Flashing Folder with a question mark in it. Here's what I get.
iMac 27″, macOS 10.14
This is Apple's guidance for creating a bootable USB installer: Create a bootable installer for macOS - Apple Support
To create this installer you will need to use another Mac that qualifies to run macOS Catalina itself.
(It doesn't have to be running Catalina, but must be capable of it.)
Looks like you have a broken partial installation there. You will need to erase that volume and try reinstalling macOS onto it.
Cannot Make the T7 my Default Boot Drive. Won't load Catalina. Help?
