Use Signal. Get your friends to do so. What you are describing is a multi-platform ecosystem so don't rely on one of the platform vendors to enable something for everyone else.
Or better, use matrix/element if you can (the backbone technology of Beeper). It's an open protocol not beholden to one central server (Signal/WhatsApp/Telegram/Discord) that could go out of business, get bought, or change their usage policy at any time.
