I was looking at Full-disk encryption performance in Librem 5 and think that it might be better to post it here, since this is about emergency calling from the lock screen, assuming that this includes the lock screen that appears when you first boot the phone.
It should be possible to boot the phone and make emergency calls without having to enter a password or PIN. This means storing part of the operating system and essential parts of the network configuration outside of the encrypted partition. All of this unecrypted data should be read-only prior to entering the correct PIN (assuming that the disk encryption key is decrypted via the smart card) and hashed and verified (or cryptographically signed) to protect against “evil maid” attacks.