SVG icons with with <DOCTYPE svg> not loading

Hello,

While using a popular icon theme, Breeze from KDE. A few svg icons like "edit-copy" wouldn't load.

The QML is :

import QtQuick 2.15
import QtQuick.Controls 2.15

        Button {
            icon.source: "qrc:/edit-copy.svg"

        }

The same with icon.name

The error is :

file:///home/cyril/Devel/Qt/5.15.1/gcc_64/qml/QtQuick/Controls.2/Material/ToolButton.qml: QML IconImage: Error decoding: file:///usr/share/icons/breeze/actions/24/document-close.svg: Format d'image non supporté

"Format d'image non supporté" is french for "unsupported image format"

After comparing the source file with another working icon, I found this header breaking the SVG :

<DOCTYPE svg>

As a workaround, I can copy the whole Breeze theme and strip all icon files of this line.

Couldn't the SVG parser ignore this header ?

If not, is it an error from KDE ?

You will find a quick test project as attachment.

Thank you for your time