[PeterT]

On my chromebook I modified the desktop launcher file. I use the following script

#!/usr/bin/sh
#

cp /usr/share/applications/calibre*.desktop .

for file in calibre-gui calibre-ebook-edit calibre-ebook-viewer calibre-lrfviewer ; do
        echo Editing ${file}.desktop
        sed -i -e 's/^Exec=/Exec=env QT_QPA_PLATFORM=xcb /g' ${file}.desktop
        echo Installing ${file}.desktop
        sudo desktop-file-install ${file}.desktop
done

I run this script after each install and upgrade of calibre.