With Cryptomator, the key to your data is in your hands. Cryptomator encrypts your data quickly and easily. Afterwards you upload them protected to your favorite cloud service.

Official website: https://cryptomator.org/

https://cyberduck.io/ - Cyberduck | Libre server and cloud storage browser for Mac and Windows with support for FTP, SFTP, WebDAV, Amazon S3, OpenStack Swift, Backblaze B2, Microsoft Azure & OneDrive, Google Drive and Dropbox

Boxcryptor - https://www.boxcryptor.com/