You can hold the phone like a digital camera and press the hardware button (even with gloves) to take a photo instead of having to touch the screen. You can also start the camera app fast and without unlocking the screen to take a quick snapshot.
I don’t think it’s possible with FP(O)OS - at least not without additional software - but on Lineage OS it is.
Sounds like your camera module doesn’t work as it should. Did you already try to disassemble it and clean the connectors?
Also do you have the old or the new camera module?
PS: I moved this to a new topic as none of your questions were really on topic about the feature request discussed in the other topic.