Good news: I was able to compile and run
evopedia, an offline Wikipedia viewer, on the Onyx Boox M92.
evopedia includes a Qt GUI, but I am not sure if this is usable on an ebook reader. This GUI is used for article search, configuration and to display a map. The articles themselves are displayed by running a browser which contacts an internal webserver. Since there is no usable multitasking interface on the M92, switching back and forth between the evopedia GUI and the browser is not an option. Fortunately, the application can be controlled via the webserver and actually searching for articles is already implemented on the webserver.
To sum things up, I think I can upload a usable version of evopedia in the next days.