I hate to pile on, but you're putting up a lot of barriers that are going to discourage casual viewers. I don't want to sign up for some app I won't use for anything else. I don't want to give out my email. I definitely don't want to pay for anything. Maybe I'm not your target market, but this is going to be a hard pass for many people.
The WhatsApp API is not as open as Telegram's, you have to apply and pay and so on AFAIK. IDK about signal but feels even more nichey than Telegram. I want to focus on doing one channel well than then expand to others