Maybe "rclone" is a good choice for you. There is also a GUI for it, called "rclonebrowser". It supports encryption and cloudstorage can be mounted into the file system.
I am using it on my Linuxsystems next to the Boxcryptor-portable-Client, because the BC-client is not very usefull for large offsite-backups.
https://rclone.org/
https://mmozeiko.github.io/RcloneBrowser/