!Hubzilla Support Forum
I ran across this today as I was trying to find a way to move 12+ Gig of data up onto a ZAP instance. It works really well. I used it (actually - it's still uploading, so I guess I AM using it) in the Windows Subsystem for Linux - mostly because I'm a Linux Geek and also because I didn't even think about installing it natively on windows until later.
It's a command-line tool. They have an experimental GUI being worked on as well. It interfaces with WebDAV and 35+ other remote end file store type things (S3, SFTP, etc. etc.). It has the ability to MOUNT a WebDAV store with a cache (haven't played with this, YET). Overall, it looks VERY promising. Rclone
Rclone syncs your files to cloud storage: Google Drive, S3, Swift, Dropbox, Google Cloud Storage, Azure, Box and many more.