> RCS may require access to certain SIM card information, which only pre-installed apps can do
> because they don't want to implement RCS themselves.
Sounds like they can't implement RCS themselves even if they wanted to, not simply that Google doesn't provide an open source implementation? (Referring to app developers here, not custom ROM devs.)
They can't implement RCS for every carrier, but they can implement it for some. Others require nothing more than a network call to a predefined HTTP address over a data connection.
Although Google may dislike it, I don't believe Google's RCS implementation (the one most of the world uses) requires elevated permissions. Their activation sequence is proprietary and closed source, though so I'm not 100% sure.
Just having a base implementation for custom ROMs would be a start. Given that Google will block custom ROMs from RCS in their app (I believe because the spec says to), there is a need for an independent implementation if this makes RCS popular enough under American users.
Someone will have to inventory the activation mechanisms for each carrier to see if there really is a disadvantage. I'd start with mine, but all of the carriers in my country have shut down their RCS servers a decade ago.
I am not familiar with RCS, but considering the plethora of messaging apps available that just work, why did they choose the most complicated way for users to use it? And what do you mean it is not available on every carrier and needs SIM access?
I haven't seen any indication of that at all. There's sort of an API, but it's basically restricted to Samsung's messenger only.
The EU won't get involved unless a significant chunk of the user base uses Google Messenger. I don't think EU users will reach that threshold because most of the EU uses basically any chat app except for SMS/MMS. Things like receiving verification SMS messages still work using the existing API and I have a feeling that that represents the majority of SMS use in the EU.
Is that a planned feature? It's frustrating that third party messaging apps don't work with RCS. I hope we don't have to get the EU involved here...