Laravel backup - Copying zip failed because: There is a connection error when trying to connect to disk named `S3`

Question

I'm trying:

php artisan backup:run --only-db -vvv

But get an error with no detail as to what the issue could be:

Copying zip failed because: There is a connection error when trying to connect to disk named S3

The -vvv doesn't seem to have any effect, how do I get more details for this error?
Or how would I debug this?

Answer 1

Sometimes the act of writing the question and actually pushing the Post button triggers some additional thinking even after one seems to have exhausted all avenues.

Case matters - my config/backup.php had an uppercase S and my config/filesystems.php had a lowercase s (the default).