Accessing WhatsApp iCloud backup?
The short answer is via iCloud Drive.

Your WhatsApp backup(s) are stored in a hidden folder of iCloud Drive on your MacBook (if you signed into iCloud and turned on iCloud Drive).

To find your WhatsApp backup(s):

Launch Terminal (in /Applications/Utilities folder)
Type the following commands

cd ~/Library/Mobile\ Documents/
find *whatsapp*


You should see all the files related to your WhatsApp backup(s).

If you don’t see anything, then make sure that iCloud drive is turned on.
If you only see *.icloud files, then turn off “optimize mac storage” in the icloud system preferences.

To my knowledge, you can’t access directly the messages as they are stored in an encrypted SQLite database.

The documents, pictures and videos are stored in separate, unencrypted archives:

Document.tar (PDFs and other attachments)
Media.tar (pictures)
Video.tar (videos)
To extract what’s in there, copy those files to your desktop via the following terminal command:

cp *whatsapp*/Accounts/*/backup/*.tar ~/Desktop


Then, double-click on the .tar files to extract a folder structure containing the files organised by conversation.

Note: If you have multiple WhatsApp accounts backed up to the same iCloud account, you’ll need to replace the ‘*’ between “Accounts/” and “/backup” by the desired phone number.

Hope this helps!