I would still assume that with apps like Snapchat, there are inherent problems on meta-level (from an E2EE view) because for the users, Snapchat is essentially a trusted third party, providing governance/management features. But it can well be that Snapchat does not provide E2EE; I cannot see any remarks about it on their webpage.

However, on the WhatsApp webpage, you can find the E2EE hand-waving that I was alluding to: https://faq.whatsapp.com/820124435853543

"WhatsApp _considers_ chats with businesses that use the WhatsApp Business app or manage and store customer messages themselves to be end-to-end encrypted."

And later, they write that in many cases, Meta can actually read the messages.