only rclone can decrypt such a file.
With all due respect, the encryption is open source and there are at least a few tools that have reversed it (see for example crypt_rclone and rclone-js).
However, it is almost certainly easier just to use rclone to decrypt it.
To @ppohoda, I wrote a HowTo Guide for using rclone for one-off decryption; though I only tested it on Linux and macOS.