So, I have two user accounts, a default one with no google apps installed, and a secondary one with sandboxed google apps. The secondary one, I have set the default camera to be the google pixel camera app*. Double pressing the power button works fine, when the phone is unlocked.

If the phone is locked, double pressing the power button does not work, it instead opens the lock screen, I enter my password (for the secondary user account), and I get the app select modal with the option to use the graphene OS camera Just Once / Always, or the Pixel camera below (no option to set default).

Any thoughts on how I can make the double press open the pixel camera?

If I'm using the primary account (with no pixel camera app installed), the double press opens the GrapheneOS camera without an unlock required, exactly as I'd expect.

(*The only reason for using the Pixel camera app is that it supports RAW and the GrapheneOS camera app does not, which unfortunately is important to me.)