When I press download report, I get a zip-file instead of an iXBRL file, but how can I download the iXBRL file?

iXBRL does not have a single file format, and because it contains both visual and technical layers, it is delivered in a zip-folder containing both the technical and the visual parts. So, the zip-file you download is your iXBRL or ESEF report, and it is what you need to hand in to your local authority.