one possible workaround is to use rclone mount, which makes cloud storage appear as a local folder.
then use any dedupe tool you would use for local on that mount.
if you are worried about having to download the files to calculate the hashes, you can use a free/cheap virtual machine from google cloud.
for google cloud compute virtual machines, there are not ingress/egress fees to access gdrive.
https://cloud.google.com/vpc/network-pricing#egress-to%20service