I've made one such frontend for not only backblaze but also Nextcloud (via webdav), and pretty much every protocol like FTP, SFTP, S3, ... It's all open source:

I've made one such frontend for not only backblaze but also Nextcloud (via webdav), and pretty much every protocol like FTP, SFTP, S3, ... It's all open source: https://github.com/mickael-kerjean/filestash https://github.com/mickael-kerjean/filestash