Fastmail

Europe has historically been charged by the text message, the US not so much. So SMS became dominant in the US primarily because of that, but also because it’s the lowest common denominator and everyone supports it, no matter what phone you have.

Yeah they really could be doing a lot more on that front

It is an Apple problem.

Don’t confuse a client API with a cross platform protocol. They are different beasts and Apple refuses to send or receive RCS messages. That’s different than a client trying to send or receive an RCS message.

Apple is vetted as an authorized entity whereas a random client is not.

No, there is nothing. Google has no API into RCS so it’s a closed system, same as iMessage unfortunately