with all due respect, the one that don’t seem to understand is you, despite already being said to you above:
it was already explained that this is not the last time their interacted with the app, but when they sent you a message, there is no point in having a toggle for this information because the date is there already anyways, in the last message they sent you or the timestamp of the read receipt etc
many more want to see it, and asked a lot for these “online” presence features, that is why WhatsApp etc. have them after all, the last-seen info helps for example to decide if a contact should be removed from a group because it was last-seen 1 year ago etc. without that you wouldn’t have a way to know inactive contacts
also adding an option is completely useless, since as already was explained this is nothing related to a central server, but just information that is already available, there is no option in the world that can make you prevent another person from knowing that you sent them an email 20 min ago, it is like saying “I want to send a message to a contact but they shouldn’t be able to know at what time it was sent”, they will always be able to get that information, manually or via 3rd party clients etc.
on the contrary, exactly because Delta Chat is a private messenger, and privacy here means you can chat with family and close friends in private without 3rd parties eyes, not that you can hide from your mom when was the last time you sent her a message
I think the problem here is that people see that “last seen” and are immediately worried because they think it works like on WhatsApp and other people can know when they are online, the only thing you need to explain to them is that here that option works different in a more private way and no one can know they are online if they don’t send a message to them or in a group where they are (that basically it only reveals it when it is obvious because you are sending a message, reaction, etc.)
if you are using Delta Chat to chat with untrusted people you don’t want to reveal your online status, then no option would save you there because such untrusted malicious contact would be always able to figure out your last-seen, but as said, that is only when you sent an email to them so you don’t really need an option, just don’t interact with the person and they will not know, if you interact they would know even without that last-seen field