Answer by Joseph Smith for How can I view a progress bar when running rsync?

This finally worked:

rsync "$rsync_param" -a --prune-empty-dirs --exclude "*.iso" rsync://archive.ubuntu.com/ubuntu/indices/ /repo/ubuntu/indices | pv -lep -s $(rsync "$rsync_param"n rsync://archive.ubuntu.com/indices/ /repo/ubuntu/indices | awk 'NF' | wc -l)