my understanding is that meta doesnt have the keys...it's only at the client but am I mistaken?
Discussion
Leaked Federal Bureau of Investigation Lawful Access papers
Whatsapp's information for Law Enforcement Authorities:
https://faq.whatsapp.com/444002211197967/
Rolling stone article:
I recommend checking out this website that compares different messenger apps:
https://www.securemessagingapps.com/
Generally the less information the platform is capable of having the better.