I haven’t figured out how rk activate that on my own WhatsApp, so while you’re right, I don’t think it’ll be quite that easy.

A way to keep control over your data is to run XMPP/Matrix bridges that a) unify all your messages into one single app and b) keep a copy of those messages under your control.

Doing this yourself requires quite some Linux skills (and a domain). You can use hosted services like Beeper but as far as I know, hosted services all respect deletion requests from the app and a service banning you could easily send a million delete requests to clear out your chat history.