Yeah I know..."why are you using Google products on degoogled GrapheneOS...blah blah blah." Anywayyyy
Partner Sharing allows you to automatically share uploaded photos with a "partner" Google account and the shared photos don't use the partner's Google storage. I have my main Google account share all photos I take with a partner account. So each photo I take is both automatically uploaded and then automatically shared.
While the automatic camera upload works, the photos I'm taking on GrapheneOS are not being shared to my partner account. This is true for both the default grapheneos camera, pixel camera, as well as manually sharing photos to the Google Photos app.
I tested this on another up to date pixel device running stock using the same Google Photos settings and partner sharing still works normally on that.