Are STOL (short take off and landing) aeroplanes possible with 1900s and 1910s tech ?


They're monoplanes, the Sopwith Camel is a biplane, which I presume generates more lift, that could explain it.
They all flew off of grass fields.
so they could always take off into the Wind

So when surfaced airfields came about, that's a problem, may not always be into the wind, but crosswind
And the Camel, and most of the other WWI fighter aircraft, were very spotty on inherent stability on any axis of movement, like almost none, had to fly it every second.