How to copy the entire contents of a Time Machine backup drive to a new one?
The best method to copy (if possible) a Time Machine disk hfs+ to a new one is given by Apple here : https://support.apple.com/guide/mac-help/if-the-time-machine-backup-disk-is-full-mh15137/10.15/mac/10.15
You copy the directory Backups.backupdb from the old disk to the new one by the Finder. It's very long but effective.