The usage guide says that
Pixel Camera (previously known as Google Camera) can take full advantage of the available cameras and image processing hardware as it can on the stock OS and does not require GSF or sandboxed Google Play on GrapheneOS. Direct TPU and GXP access by Google apps including Pixel Camera is controlled by a toggle added by GrapheneOS and doesn't provide them with any additional access to data.
But I can't find this toggle. Where do I find it? Is it still true that GSF is not required? This comment seems to suggest otherwise, but it may be wrong.