Thanks! Is it Rayalot's post on 12th Feb you are linking to? Unfortunately that doesn't seem to work for me.
The settings menu layout seem to have changed since that post (new Android version?) but using the search function to pick out the individual aspects:
- "Allow camera access when locked" is already enabled
- "Quickly open camera" is already enabled
- I can "Clear default preferences" for Graphene Camera
- Pixel Camera doesn't have "Clear default preferences", probably because it isn't the default for anything on my phone (but I'm guessing)
Having cleared the default preferences for Graphene Camera, I double-click the power button with the phone unlocked and get asked to choose the app to complete the action. I choose Graphene Camera and pick Always. Double-clicking with the phone unlocked now opens Graphene Camera, but if the phone is locked I get asked to enter my password as before.
Rayalot is talking about OpenCamera and I am trying to have Pixel Camera as my secondary app - I appreciate you probably realize this and that's what's working for you, but I wanted to point it out in case that's the difference between it working for you and not for me.
For what it's worth - since treequell mentions it earlier in that thread - I do have camera access enabled in the quick tiles.
Incidentally, I tried again but making Pixel Camera the default instead of Graphene Camera and it doesn't make any difference - I still get asked for my password if I double-click while the phone is locked.