Air Explorer - Air Explorer is a software to manage all your multiple cloud drives (like Dropbox, Onedrive, Google Drive, Mega, Mediafire, Box, Hidrive, Yandex, Baidu,...) as well as WebDav and FTP connections.
CloudGopher - Copy email, files & more across Google accounts
ExpanDrive - ExpanDrive is a fast network drive and browser for cloud storage.
odrive - odrive aggregates all cloud storage. Access, sync, share, and encrypt everything in one place. Integrations to 20+ storage services, desktop sync, Linux support, placeholder files, zero-knowledge-encryption, web client, advanced sharing, and more!
MultCloud - Multiple Cloud Storage Manager: Migrate, move, sync, copy, backup and transfer cloud files with MultCloud, which supports Dropbox, Box, Google Drive, Mega, OneDrive and FTP, etc.
Yandex.Disk - Files on Yandex.Disk won't get lost if your phone or computer breaks.