

I’m not sure there exist any.
Last time I checked, this was actually the biggest criticism Google recieved. They were pushing RCS on Apple, yet keeping it proprietarily only available on Google Messages.
Maybe it has changed. I don’t know.
Latest update I heard was that they made it ON by default in Google Messages.
Isn’t Firefox open source? So isn’t it possible that anyone could see the changes being made even in the nightly versions? I’m not a programmer so forgive my ignorance.