How to run FlashPrint v4 on a machine with Qt > 5.9.5

Download and install Qt 5.9.5 in /opt/Qt. Change /usr/share/applications/FlashPrint.desktop file to run FlashPrint using that older version of Qt.

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Exec=env LD_LIBRARY_PATH=/opt/Qt/5.9.5/gcc_64/lib /usr/share/FlashPrint/FlashPrint
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