I am sorry for my late reply. Here is the workaround that I can suggest: Loop through all the front end pages and un-publish those which are not available in Czech language. They should be unpublished in invariant culture too.
PageManager manager =
var pages = manager.GetPageNodes().Where(p => p.RootNodeId == SiteInitializer.FrontendRootNodeId);
var defaultCulture =
Please understand that switch of default culture is not a supported scenario and manipulating the pages through scripts is risky. Please backup you database before you execute the script.
If you have other questions, please let me know.
All the best,
the Telerik team
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