splice0370 Is there any way to make [Google] Camera open when double pressing the power button without having to unlock the device please?
Yes, absolutely. After double pressing the power button, and selecting to always open the Google Camera app, it should work fine on subsequent occasions. Not sure if it's required, but I suggest double pressing the power button whilst the phone is unlocked to be able to select the appropriate option.
Repeat the process whilst the phone is unlocked to be able to set Google Camera as always open.
If you're still having issues, you can clear all open by defaults settings for the GrapheneOS Camera app, in its app info. That might also help.