What a surprise when i discovered that you don’t seem to need to backup Whatsapp messages any more. They apper to be stored on Meta servers. I’m sure it was not like this in the past? My wife left her GrapheneOS phone on the roof of the car and drove off. I managed to recover it but it had been ridden over by i car. So boight another pixel and installed Whatsapp again. She can’t live without it as all her clients are on there. When i setup Whatsapp on new phone, all messages appered again, just like that. Spooky … I think in the past it wasn’t like that?
https://snee.la/posts/the-workings-of-whatsapps-end-to-end-encrypted-backups/
This is my analysis of WhatsApp’s backup mechanisms. The best possible thing you can do from a privacy PoV is to enable end-to-end-encrypted backups, which is disabled by default.
As far as I know, WhatsApp’s backups don’t go to meta’s servers, but instead google cloud / icloud. If your wife logged into her google account before, had backups enabled (frequency is weekly afaik), and signed into the google account again on the new phone - WhatsApp will restore the backups from the cloud.
If you enable E2EE backups, then you’ll be asked to enter your password, which only you can have. If you fail to supply that, your backups are lost forever. The implantation is a bit scuffed IMO, but still better than nothing. Things may have changed since I analyzed it in 2022.