I wasn't sure how many people were aware of this, so I thought I'd share.
While the Pixel Studio app itself doesn't function on GrapheneOS, it does have a built-in screenshot editor which works perfectly fine. This is the default behavior on the stock OS, as from what I can gather newer models don't use the "Markup" app for screenshot editing anymore.
The Pixel Studio's screenshot editor has a much nicer interface, more tools, and with network permissions disabled doesn't show any AI stuff.
https://play.google.com/store/apps/details?id=com.google.android.apps.pixel.creativeassistant