Regarding the post processing discussion:
Maybe some would disagree, but here is my take, as I shoot RAW exclusively these days - I finally have the neatest equipment I could even dream of 30 years ago, and I want maximum quality potential for my snapshots
There is processing, the kind that simply "develops" the modern equivalent to film and adjusts exposure and contrast values.
In a traditional photolab a color filter would have been used to then also adjust color values.
Then there is POST processing, where you take finished images and do something with them, like a collage, or twisting parts of an image into twirly thingies, etc.
In other words, it is a question of the modern equivalent of "processing and printing" to recover the scene as shot in camera to get as close to "natural eye appearance" as possible, vs. pure special effects.
I think it should be made clear what type of processing is talked about and specified in challenges, as a blanket statement could even keep RAW shooters out. And the older Sigma DSLRs can only do RAW if I remember right