So GrapheneOS is derived from Android. So I think in order to have to support for it, first there will need to be android support in Qubes.
There are ways of running it in Qubes already but it’s not very well integrated yet (I’ve had android VM myself). Some related threads:
So maybe following the same steps but for graphene OS may produce some results. But it will take considerable effort.
Other than that I’m not aware of any other effort in this direction. (would like to be proven wrong).