Hey @ktm_ ,
One of two things may be the issue:
1. When installing Clover to the USB drive, you didn't select all the options like in the guide; or,
2. The installer didn't install macOS correctly.
Try reinstalling Clover first, and make sure the options are exactly like what I have in the guide (step 4). If that doesn't fix it, reinstall macOS and make sure the drive has a partition scheme of GUID Partition Table, and the partition you're trying to install on is APFS or Mac OS Extended (Journaled).