What is this U folder under root /?
Catalina creates a read-only volume for System files, including the root level. You can't write to root level while booting from that volume.
Normally, when Catalina is installed, the installer moves any third-party or user folders away from root level. It's not clear why that hasn't happened, unless the datestamp is not accurate.
- Disable SIP: Recovery mode, Terminal:
csrutil disable - Restart.
- Mount drive for read and write
sudo mount -uw / - Delete it
[sudo] rm -rf /your\ folder\ - Restart.
- Enable SIP: Recovery mode, Terminal:
csrutil enable