I don’t understand how a smartphone app could theoretically support non-custodial lightning in a trustless manner. If you accept a payment through a channel, the other side could try to cheat and close the channel with the old state. If you don’t open the app for a long time, it won’t connect to the internet and won’t discover this cheating attempt on the blockchain.

Of course that if you do trust the other side not to save old states, then even if a government takes over the servers they can’t revert the state - which is better that custodial lightning (which may also have only fractional reserves and who knows what).