@kenbarbi @sam_uk @Abhishek Many thanks for your anwser.
You have to choose between the RACHEL module “Wikipedia for Schools” and the additional Wikipedia modules.
“Wikipedia for Schools” is just a small selection of Wikipedia articles. These are stored as static html files. Skylark’s web server can only handle static pages. This is sufficient here.
But I want to use the additional module “de-wikipedia” or “en-wikipedia”. However, these modules use dynamic php files. Skylark’s web server can’t handle this. The articles are stored in zim files. zim files can also be read with the software kiwix (https://www.kiwix.org/en/downloads/).
It is possible to install the kiwix reader in Skylark?
BTW: There are extensions for Firefox and Chrome. After the installation you select under “Configure” all *.zim?? files and has the complete Wikipedia under “Home”.