Extracting isn't the hard part. I have yet to figure out how to append Whatsapp message from a previous backup which I have held for 8 years.
The iOS backup was corrupted and I had to start over again at the time. The Whatsapp file was extracted but I never got round to it. ( Along with important pictures inside the Whatsapp)
To this day I still blame on it on iOS backup problem. Which is still a thing in 2022.
I wonder why Facebook hasn't made an iOS to Android Whatsapp history transfer a priority. To most people outside of US, Whatsapp history transfer is the biggest lock in with the Smartphone ecosystem.