Don’t worry, I did not end up in the gutter. But I did install a rain gutter today;

In case you have a hard time seeing the gutter; that’s because it’s brown. Mounted on the fascia boards. Rather flimsy aluminum, but at least aluminum so it won’t rust or crack.
It will prolong the life of my deck boards, as the rain and condensed water will now be funneled off to the side.
Instead of an ugly down drain, I simply opened up the right end cap so that water can poor out that side. It should hit just off to the right of the deck. There should be little leaves and other debris in the gutter as there are no trees taller than my home nearby.
And yes, the gutter is mounted slightly non level, allowing water to run off to the right side.
Maybe there will be a thunderstorm, in which case I can check if it works as intended.