[honestjohn]

It's about as secure as any other non-E2EE chat or other kind of service, except it also has E2EE mode, which is limited to 1:1 chats for fair reasons. Plenty of other services advertise themselves as "secure," which doesn't mean a lot. So I don't see anything misleading there.

Aside from that, I don't trust Telegram or its CEO at all, partially because of what you said about open-sourcing (or not) and partially because of his ties to Russia and Azerbaijan.