GrapheneOS Camera has HDR+ on Pixels. It's a less aggressive variant of HDR+ than what's used by Google Camera. It captures and combines fewer frames than Google Camera tends to use at the same light level so the photos look more natural but it doesn't reduce noise as much.

GrapheneOS has the same camera features and quality as the stock Pixel OS within the same apps. It's your choice if you want to use Google Camera for the full feature set. You still have HDR+ without it. Night, Portrait, etc. will be available in GrapheneOS Camera eventually too.

GrapheneOS Camera app will have more of the features in the future too. It already has multi-camera zoom since the Pixel 4, a light form of HDR+ since the Pixel 2, HDRnet for preview since Pixel 4a, EIS, etc. HDRnet for video likely works fine everywhere it's supported too. This will come as the CameraX API evolves and as Google adds the required vendor extensions. (Samsung users can already see how full featured GrapheneOS Secure Camera is as they've already provided these for their devices.)

These should come with Android 14 for some devices and/or the Pixel 8. However, it may initially require sandboxed Google Play.

That said Google Camera with all it's features can be used without sandboxed Play Services installed and with improved privacy by disabling permissions including network. (Sensors will stil be required for orientation however.)