If, as it seems, the set is not (any longer?) available from specialist retailers, it can also be purchased directly from Noctua, providing proof of purchase of the cooler and an AM4 motherboard/processor (order form is linked in the article): https://noctua.at/de/nm-am4-l9al9i-mounting-kit

For office, light gaming, etc. the cooler is easily sufficient. However, since the cooler was only designed for up to 65W TDP, you will tend to have worse temperatures/thermal throttling with VERY CPU-heavy applications (CAD, rendering, etc.) and should fall back on an alternative (with the same height, switch to an AiO). Of course, manual OC (voltage reduction, etc.) would be possible to keep the i5 9600K in check a bit or limit the package power to e.g. 65W.

Yes, that's easily enough as long as it's not overclocked. Anything is better than the original cooler ;)

hello, if i'm not mistaken, the slim 94mm fan comes with this cooler. so it could be that the screws are too short or the bracket doesn't fit. if you don't like noctua and need a smaller cooler because of lack of space, then i recommend the silverstone ar06, which is 58mm high. Unfortunately, it is not in stock at digitec. And another tip: the performance of the noctua coolers is not only based on the good quality of the heatsinks but also on the super fans.