> Last I checked (about a year ago I think) Whatsapp backups were platform-locked as well.

I'm not sure why you are being downvoted. Whatsapp backups are still platform locked to this day. But that may change soon.

https://www.businessinsider.in/tech/apps/news/whatsapp-may-s...

Not completely. WhatsApp pushed out an Android-compatible backup option on their BlackBerry 10 app when they announced that they were shutting the app down a few years ago. But it was behind a notice that said it was 'not supported', even though it worked fine. Only to Android though.

They are working on it https://9to5mac.com/2021/04/05/whatsapp-chat-history-migrati...

You can get a dump of all your messages with someone pretty easily.