I haven't had luck or even tried. Mostly, people won't know what RCS implies. But there are still important differences that Signal brings to the table. Signal is not merely E2EE on communications. Signal is actually a combination of many privacy protocols to ensure private communications, where E2EE is only one of them. They have a lot of protocol innovations in key exchanges, group management, metadata storage, contact discovery, etc. RCS does not guarantee E2EE, it needs to be implemented by the ISPs, so using it you don't really know if the other end's ISP supports it, so the RCS negotiation will downgrade to the common denominator.

Your address book is uploaded to Facebook servers when you use Whatsapp. And each time you interact, they know with who and link this information with other profiles and users of the Meta products.

I'm surprised at Telegram, I expected more information to be available, since it's a central database with all conversations. But I can see how they simply don't collaborate and protect by obscurity making data unavailable.