While there already seems to be a thread covering the modification of the Goobay 67269 LNB and a great article by DH1DA, it seems that the manufacturer has changed the PCB layout completely. Since I ordered a larger amount of these, I ended up modifying them from scratch. I documented the modification as well as I could. I will follow up with measurements regarding frequency response and gain figures. The PDF can be downloaded from the link provided below.
Blog (shortened version): https://baltic-lab.com/2023/07…-100-satellite-reception/