starglider Whether a phone may be compromised in other ways are irrelevant.
Having these options in the app heavily implies ephemeral messages will work for both sides 100% of the time in the app itself. Why? Simply because it is advertised in the app extremely clearly to the both sides at the start of a conversation and throughout.
Pay close attention to the language used below.
Quote from Signal Support page: "The message will disappear from your devices after the timer has elapsed. This is not for situations where your contact is your adversary — after all, if someone who receives a disappearing message really wants a record of it, they can always use another camera to take a photo of the screen before the message disappears."¹
This is the app recommended by CIA? Really?
1: https://support.signal.org/hc/en-us/articles/360007320771-Set-and-manage-disappearing-messages