Sorry, but I don't I agree with the wording, "even a charcoal one".
IMO the use of a charcoal BBQ in an awning is the more dangerous of the two, from carbon monoxide levels.
For years the frame tents we used featured kitchen areas, here they were designed for gas hobs. From a monoxide issue it is provision of adequate to over provided ventilation that seems to be the critical requirement.
All said, on every count it has to be safer outside with gas, and charcoal BBQs should never be inside.
I agree that charcoal is potentially the worst, as many people think CO is only produced by a compromised flame, so the lack of an obvious flame belies the danger.
But also many gas BBQ's allow fat and juices to drip into the flame and onto the burner bar and can compromise the flame pattern. Anything that causes the flame to produce orange or yellow tips or even complete flames is producing high levels of CO. It's this corruption of the flames that helps to produce the authentic BBQ flavours.
Proper camping cookers will have been designed and tested for compliance with the emission regulations, and as such will produce minimal amounts of CO, and that will continue as long as they are maintained and used properly. when used in kitchen tents with good ventilation, and appropriate fire precautions should be OK. But BBQ's are not the same as cookers and the risks are much higher not only from CO but also from fat splatter and the possibility of ignited fat droplets being ejected and set fire to nearby materials.
I maintain the advice not to use a BBQ inside an awning.