Well, I’ve come across a workaround that seems to work, in spite of the deficiencies in this product!
I followed this link for a way to back up using WSL (Windows Subsystem for Linux), and although the accepted answer (No, you can’t do that) doesn’t fill the bill, if you keep scrolling down, there is another option: make use of DrvFS to mount your drive that the My Cloud Home is on, then copy the files any which way you want to wherever you want. In my case, I set up a remote NextCloud on a raspberry pi, and mount both drives in WSL, then use rsync to copy everything from the My Cloud home to the NextCloud. Actually pretty easy!
In the bash command line, create the mount point for your My Cloud Home, “sudo mkdir /mnt/z”. Then, use the “sudo mount -t drvfs Z: /mnt/z; rsync -avzh /mnt/z /mnt/c/Users/username/Nextcloud” and it should take care of all your files from the My Cloud to the NextCloud. You could sync to any location you want, really (Google, OneDrive, wherever). Anything that maps a drive or directory in Windows. You could store it locally on the Windows computer, too, if you’d prefer. Just have a remote computer that has a connection to the My Cloud Home and rsync to a local directory.
This is a quick overview, but if more specific instructions would be useful, I think I can put together a step by step of the whole process (including setting up your own NextCloud).