> I don't really see how it's possible to mitigate client compromise
Easy: pass laws requiring chat providers to implement interoperability standards so that users can bring their own trusted clients. You're still at risk if your recipient is using a compromised client, but that's a problem that you have the power to solve, and it's much easier to convince someone to switch a secure client if they don't have to worry about losing their contacts.
You seem to think the government wants your messages to be private and would "pass laws" to this effect.
Methinks you put far too much faith in the government, at least from my understanding of the history of cybersecurity :)
> Easy: pass laws requiring chat providers to implement interoperability standards so that users can bring their own trusted clients.
In Europe that's called the Digital Markets Act.