How to confirm that a cloned external hard drive is accurately cloned?
I've found a way to use some command line tools to recursively check hashes of the individual files. Here's my commands:

hashdeep -rel -r . &gt; hashdeep-outout.txt

Hashdeep (which you can install via homebrew) will create a CSV file listing each individual file with various hashes including MD5 and SHA256. -rel lists the files with the relative path to the CWD, so I can run this command on both the old drive, and the new cloned drive, and the file names will be identical.

sort --field-separator=',' --key=4 hashdeep-output.txt &gt; hashdeep-sorted.txt

This sorts the CSV file by filename (the 4th field), so that when I compare the two files (for the old drive, and the new drive) everything will be in the same order.

Then I use just diff to compare the sorted output files. If there is anything which was copied incorrectly, it will let me know because the hashes won't match up.