I would rather have better E2EE

and

I want my chats to be available on all devices even if I drop my phone into a volcano

are kinda conflicting goals. If the chats are easily available on a new device without you manually syncing the key, that means the key exists somewhere in the cloud outside of your control, which is the opposite of good E2EE.

You can still achieve both goals, but it would involve you exporting the key, storing it somewhere, and then importing it to a new device from where you stored it.