Officially, no, there is no other method other than Safepoint / Backup within the My Cloud single drive Dashboard to backup the My Cloud to a USB hard drive attached to the My Cloud USB port.
Unofficially, there are a number of methods, from using software on your local PC (like Free File Sync - https://www.freefilesync.org/) to using SSH within the My Cloud firmware to create an Rsync (or similar) copy function to the external USB hard drive. You can find a number of past discussions on alternatives to Safepoint / Backup by using the subforum search feature, magnifying glass icon upper right. Here is one such discussion:
https://community.wd.com/t/happy-accident-includes-an-alternative-to-safepoint/96152
