But where will you put the server? Not in the USA, that's for sure. Not in the UK. Not in Europe. Maybe you can broadcast your encrypted messages illegally on shortwave radio, until the FCC catches you broadcasting illegally on shortwave radio. Maybe you can bounce them off the moon (that's a real transmission technique) or hijack someone else's satellites (more trivial than it sounds because a lot of them are quite dumb). Or you can put a server in somewhere like Myanmar where they won't care about servers hosting E2EE apps, but they also won't care about strange men in black suits turning up and stealing servers hosting E2EE apps. Either way you'll have some difficulty.
You could just use onion services to to hide the server, and store some backup onion services (whose private keys are kept offline) within the application or its files. When the server goes down due to seizure, you spin up a new one under the backup service's pubkey, and sign a list of new backup keys which will also be kept offline until the next seizure.
You could also combine encryption with steganography, if you strip non-random 'protocol information' from your encrypted bits. Doing that, it would not be easy to prove that you are sending encrypted messages at all without having obtained your keys.
