The thing is that there's nothing actually special about SpiderOak as a service. Since the data is encrypted end to end, the only special thing is the client and as you've pointed out, there's is terrible.

On that note, once I gave up on SpiderOak I went looking for alternatives and they actually exist:

- Syncany: https://www.syncany.org/ - Java based, works on Windows and *NIX, uses S3, Dropbox, Flickr, FTP, Openstack Swift, SFTP and WebDAV as backends.

- Rclone: http://rclone.org - Go based, works on everything Go supports, uses Google Drive, S3, Swift, Dropbox, Google Cloud Storage, Amazon Drive, OneDrive, hubiC, Backblaze B2 and Yandex.Disk.

Syncany at least supports limited file versioning but not as granular as you seem to be after. The upside is that unlike SpiderOak, Syncany is open source and you can contribute features you want. If you're only after backup, there's also Borg which might work for you: https://borgbackup.readthedocs.io/en/stable/.