Extension:DynamicPageList (DPL), version 2.01 : Error: Wrong 'namespace' parameter: 'Main'! Help: namespace= empty string (Main) | Archive | Archive_talk | Category | Category_talk | Draft | Draft_talk | File | File_talk | Help | Help_talk | KDE_UserBase_Wiki | KDE_UserBase_Wiki_talk | Layer | Layer_talk | MediaWiki | MediaWiki_talk | Summary | Summary_talk | Talk | Template | Template_talk | Thread | Thread_talk | Translations | Translations_talk | User | User_talk.
Extension:DynamicPageList (DPL), version 2.01 : Error: Wrong 'namespace' parameter: 'Main'! Help: namespace= empty string (Main) | Archive | Archive_talk | Category | Category_talk | Draft | Draft_talk | File | File_talk | Help | Help_talk | KDE_UserBase_Wiki | KDE_UserBase_Wiki_talk | Layer | Layer_talk | MediaWiki | MediaWiki_talk | Summary | Summary_talk | Talk | Template | Template_talk | Thread | Thread_talk | Translations | Translations_talk | User | User_talk.
Extension:DynamicPageList (DPL), version 2.01 : Error: Wrong 'namespace' parameter: 'Main'! Help: namespace= empty string (Main) | Archive | Archive_talk | Category | Category_talk | Draft | Draft_talk | File | File_talk | Help | Help_talk | KDE_UserBase_Wiki | KDE_UserBase_Wiki_talk | Layer | Layer_talk | MediaWiki | MediaWiki_talk | Summary | Summary_talk | Talk | Template | Template_talk | Thread | Thread_talk | Translations | Translations_talk | User | User_talk.
Extension:DynamicPageList (DPL), version 2.01 : Error: Wrong 'namespace' parameter: 'Main'! Help: namespace= empty string (Main) | Archive | Archive_talk | Category | Category_talk | Draft | Draft_talk | File | File_talk | Help | Help_talk | KDE_UserBase_Wiki | KDE_UserBase_Wiki_talk | Layer | Layer_talk | MediaWiki | MediaWiki_talk | Summary | Summary_talk | Talk | Template | Template_talk | Thread | Thread_talk | Translations | Translations_talk | User | User_talk.
Testing: [[Special:myLanguage/Non Existing Page|Non Existing Page]] gives Non Existing Page as it should!
This is an old issue which I reported to Ingo and Nikerabbit as a serious nuisance, so perhaps it was fixed some time ago and I had forgotten. I've removed the Trello card. Thanks for pointing it out.