If they mandated discord as a closed support community sure, but you can't be too upset by the mere affiliation with a discord channel when they also offer all the above
If I remember correctly, their matrix channel was flooding with spam and abuse which was primarily coming from Calyx, which by the way is an terrible OS. Even a stock OS would perform marginally better in terms of security than CalyxOS
> Our chat rooms are bridged across Discord, Telegram and Matrix so you can choose your preferred platform.
> We have an official forum for longer form posts, which is publicly accessible and easier to search. We are using Flarum for our forum.
https://discuss.grapheneos.org/
If they mandated discord as a closed support community sure, but you can't be too upset by the mere affiliation with a discord channel when they also offer all the above