You could do something like this as I'm not aware of a way to change the units in the ls command:
felix@gemini:/gmedia/Movies/Unsane (2018)$ rclone ls gcrypt:Movies/"Unsane (2018)" | awk '{ byte =$1 /1024/1024**2 ; print byte" " $2 }'
24.157 Unsane
felix@gemini:/gmedia/Movies/Unsane (2018)$ du -ms Unsane\ \(2018\).mkv
24737 Unsane (2018).mkv
That's in GB.