Does it do RCS?
AFAIUI though GOS does intend on providing an RCS impl eventually even if it takes years to do.
TIL that RCS was designed as a fairly decentralized protocol where every carrier could run their own RCS servers, but it didnt get adoption. So Google stepped in and built their own routing infrastructure, and now mostly all RCS is centralized on Google's servers (even if you use an iPhone, because the RCS server is mandated by your carrier)
This just shows the fragility of the tech and why I wouldn’t want to rely on it for anything crucial.
Do NOT talk about privacy, E2EE, or any of that. To regular people, "privacy" has negative value, so even if they wanted something, your talk of private communication and not being scanned by data brokers and governments will make them want it less.
So what to do then?
I present Signal as a novelty and focus on one single feature: "hey, video calls work much better than WhatsApp! Try it out!"
Bam, instant download.
What I'm saying is if you go, "Try DuskDozerIM, let's message on there! It's private and secure, the government and large ad companies and data brokers can't read your messages and harvest your data" then you evoque a feeling of suspicion (negative value) and their response will be "look, I already have like a thousand apps, I don't really want one more".
One additional way you can confirm this hypothesis is that almost everybody has given WhatsApp access to { all contacts ; all notifications ; all permissions } but if you sell them Signal with the "privacy/security" angle and watch them install it, you will notice they hesitate for a sec and then reply "no" to contacts, notifications and permissions, as if they're suddenly trying to inhabit the conspiracy-theorist-cum-privacy-activist mindset. Which they're uncomfortable with, and don't like. Negative value.
I broadly expect third-party RCS apps to drop that though, like how essentially none support all of MMS. did you know MMS supports slideshows (I built support for this once)? 3d objects (mimetype model/gltf+json)? "timed text" (mimetype text/mp4)?
In my experience, Graphene OS doesn't make compromises.
Just because RCS can't be done without metadata doesn't mean it's a fruitless endeavor. Why not have someone use RCS to then get on Signal? That is so much better than plaintext SMS to Signal.
And for most people, RCS between Android <-> iOS is the biggest advancement in encrypted communication for the layman that I've seen since Let's Encrypt.
Google Messages is essentially the only remaining RCS client for Android and it's the only one with end-to-end encryption. It already works on GrapheneOS via a toggle for ICC authentication extending our sandboxed Google Play compatibility layer. We want to add support for it to our own Messaging app but that's not straightforward since it's not at all an open platform even to the extent of SMS/MMS.
Of course it is relevant privacy-wise (Google still gather a lot of metadata about who speaks to who and when), but that's not even the reason I'm mentioning it.
In the RCS specification, there are three lines on a killer-feature: device attestation. A server can whitelist which devices are allowed to connect to it. And of course Google uses this, allowing only Google-certified devices and Apple devices.
And then, there is actually one RCS client for Google's RCS servers. Because Google Messages doesn't use RCS, it uses a custom protocol based on protobuf. My personal guess is that this protobuf is a 1-to-1 matching with actual RCS, and it's both-way compatible. But still, that means that potentially the Google device-attestation won't work with an RCS client.
Sibling comments say that GrapheneOS plan on implementing it. I think it can reasonably work. TBH I'm expecting that giving a LLM the publicly available information about RCS on microG should give a working "send message" within a day (even when using Google apps rather than microG, it's just that the microG work explains the API). And once RCS work in GrapheneOS' message app, it should be pretty straightforward to port to microG, so yay. However I have to admit I'm not optimist about how long it will keep working. I'd say we are two years away from Google enforcing RKP device integrity for RCS, and uh, good luck passing that.
Of course, I'm hoping that, in the EU, the DMA will break this Google/Apple-only device-attestation, but I'm not aware of anyone pushing that ATM.