Everything that is permanently exposed to the weather and direct sunlight suffers from it. Here, I would be more interested in why the seating area is placed there where you wouldn't cover it anyway, or why I would then need a roof somewhere where I never sit anyway. As always, you can have a different opinion or come to a different decision about everything else. I myself have always built fixed terrace roofs, either with a glass roof or, as now, with a "dark" roof. I find it comfortable that the furniture stays dry (still exposed to weather and partially rain/moisture), you can always use this area at the house dry. In the past, we had an awning under the glass roof, equipped with a sun sensor. For me in BW that was a pointless investment and we soon stopped using it because no sensor or automation can be set as I or the hand would decide. When the awning is out, I am out of the house and it can react to wind/rain. Hardly imaginable to leave the awning out at all times, no matter where you live. Currently we also have a nice sun umbrella in the garden that could withstand quite a bit of wind; still, we close it earlier for safety reasons because the associated noises sound rather disturbing. So the basic questions remain: What is your goal and why are seating furniture outside the area where you are looking for shade? Shading alone is possible with an awning that is retracted when it rains. 24 sqm awning would be quite a beast though.

Do you really sit outside during storms or don’t you rather retract the awning in bad weather (wind sensor helps too)? Yes. Last year I installed a 4x3 m awning at my ex's place. Good quality. No problems with wind and a little rain. Lots of wind and/or lots of rain = inside anyway. Normal rain showers are no problem.

I see it exactly the same way. So far we have experience in our new building with 2 "summers" on our terrace and have never sat outside in bad weather. Basically, it is really about shade for us.

We have a middle ground between a cassette awning and a roof since our terrace is a fire brigade setup area and is not allowed to be roofed. A frame is attached on the left and right in which the awning runs. This solution is very stable and wind-resistant. Even when it rains, the awning fabric is waterproof.

Of course, you can argue and handle it that way. However, if someone wants to sit even in drizzle or not have to worry at all about whether it will drizzle, that can also be understood. Another advantage of a fixed roof is that dew does not settle on the furniture or in the evening when you want to stay outside; it is always dry. I saw this dew on our glass roof and was glad it was dry underneath. The next person has arguments for the awning or the sail and all are understandable. You just have to find what suits you without believing that it is inherently the right choice.

At our old house we had two awnings from Arabella, so back then something decent. The larger of the two was probably about 6m wide and 3.5-4m deep. I don’t remember us using it often, but it also had some roof overhang there.
Take a look at such a big thing fully extended somewhere live. I’ve been to those, too. With the cheap ones, I fear they will start squeaking soon, and the expensive ones are just expensive, plus I didn’t like that “box” that still always remains visible.
If it’s really just for sun or shade, I would buy a high-quality umbrella, and there are all sorts of shapes available. For us, it was also the case that they eventually got stained by birds, among other things, and you don’t replace such a large fabric for several reasons.
But again, that’s just my own idea, which is why I would either build something solid with glass or go for the umbrella version.