My experience is the apps are missing very fundamental features. Which would be fine... If you could use other clients. But you can't, except for email, kind of.

Like, the calendar on mobile doesnt even have a search function. What if I want to know when an event is happening? I just have to scroll and scroll until I find it? Come on now. Also no storage backup in proton drive??? What??? That's, like, 90% of the purpose of proton drive!

The lock in is absurdly restrictive in some ways too. For example, they don't support sieve based forwarding. I wanted to forward parcel tracking emails to shop app, but can't set up an automated way to do it

Yeah I was really disappointed they released their llm service before making an official proton drive linux client.