RcloneTray is a GUI for Rclone, the "rsync for cloud storage" command line tool, which runs on Windows, Mac and Linux. Using this Electron tray application, you'll be able to quickly mount Rclone remotes, open the mount location using your default file manager, and perform other operations.
Also see Rclone Browser (updated fork) for a more complete Rclone GUI.
Rclone can synchronize files from your filesystem from/to cloud storage services like Google Drive, Microsoft OneDrive, Nextcloud, Yandex Disk, Dropbox, Amazon Drive and S3, Mega, pCloud, and others (and having WebDAV, FTP and SFTP support), as well as directly between cloud storage services. It also supports mounting these cloud storage services so you can access your files using desktop applications.
RcloneTray lists all your Rclone remotes in its tray menu, each remote having a separate submenu that varies with each storage service.