How to recover a WhatsApp backup file from iCloud and transfer it to a Windows PC?

I am trying to back up data from my iPhone 6S (16GB, iOS 11.0). To back up my chats and media from WhatsApp, I backed up the data to iCloud. While the iCloud shows a backup of over 830MB, I find myself helpless to actually transfer that backup to any other medium. I want to move it to a new Android device but cannot find any effective method to do the same. I should add that installing Google Drive on my iPhone is a blocked alternative since the app requires iOS 14 and beyond. The iOS upgrade requires more than 8GB of free space on a device that has no more than 4 (12/16GB is booked by the system itself).