There are many posts here about VoIP/SIP services and how to use them on GrapheneOS. A well-known one is MySudo. About 3 years ago, a member MySudo's support team wrote in response to a question about GOS compatibility that their team was looking for solutions to many of the issues with the app within GOS.
Well, it's been 3 years, but there has been no advancements pretty much at all with GOS compatibility. I find that odd, given that many if their users (privacy/security geeks) are more likely to use an OS like Graphene than stock android/iOS.
Does anybody know if there are any plans to make a GOS-compatible version of the app? I know there is definitely interest in that, but it seems that's not something that is currently being worked on.