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A web search turned up the Qt online documentation, which suggests using Qt Assistant to organize and read help files packaged as *.qch files. That looks to be packaged by Debian as assistant-qt6....
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#1: Initial revision
A web search turned up the Qt online documentation, which suggests [using Qt Assistant](https://doc.qt.io/qt-6/assistant-details.html) to organize and read help files packaged as \*.qch files. That looks to be packaged by Debian as [assistant-qt6](https://packages.debian.org/bookworm/assistant-qt6). Alternatively, cppreference-doc-en-qch depends on qttools5-dev-tools which in turn pulls in qt5-assistant which [provides](https://packages.debian.org/bookworm/amd64/qt5-assistant/filelist) /usr/lib/qt5/bin/assistant. As an alternative in this specific case, Debian also packages what looks to be that same documentation in HTML format as [cppreference-doc-en-html](https://packages.debian.org/bookworm/cppreference-doc-en-html).