Likely won't be an official GrapheneOS channel due to moderation or bridging requirements but I am paying close attention to the encrypted Nostr identity messaging apps like Whitenoise and Keychat. For users who want the best as a messenger right now, then SimpleX is there and mature.
Useable security comes a long way. We have a lot of apps that do it all, but we need an app that feels as good to use as Telegram does.
I think encrypted messengers using Nostr as an identity could make a valuable replacement to Session since its selling point is not having an often personally identifiable identifier like phone numbers. Session has been the subject of criticisms with their crypto.
Many of these apps including WhiteNoise have an advantage that it has perfect forward secrecy when Session doesn't. Session however benefits from having an onion routing network inbuilt. Build in onion routing and you have obseleted it.
Certain apps like Keychat having their own inbuilt lightning wallet also is quite inventive. I think it could go somewhere if done right. It does what Signal tried with their MobileCoin thing but it is much less of a gimmick by lightning actually being useable. Zapping friends through the messenger like Apple Pay Cash does is a smart idea.
Some may want these to be separate apps though. I'm also heavily concerned about cryptography, although I am not a cryptographer. I still use Signal because it is scrutinised. Upcoming apps using it need a lot of review first before I make large decisions.
I will do a technical article on my thoughts in the future but it's probably less on the security front. I have a blog web page created, I just need to get a domain and a hosting to publish. I just have lots of other commitments right now.