Hello Paul,
i think you don't have Eid ul Adha 2024 vacation. ;-)
So maybe you can write a more detailed HowTo on using custom SVG image shapes than what is written in the SPPB documentation.
I tried
<!DOCTYPE html>
<html>
<body>
<h2>SVG polygon Element</h2>
<svg height="220" width="500" xmlns="http://www.w3.org/2000/svg">
<polygon points="100,10 150,190 50,190" style="fill:lime;stroke:purple;stroke-width:3" />
Sorry, your browser does not support inline SVG.
</svg>
</body>
</html>
and i tried
<svg width="300" height="130" xmlns="http://www.w3.org/2000/svg">
<rect width="200" height="100" x="10" y="10" rx="20" ry="20" fill="blue" />
Sorry, your browser does not support inline SVG.
</svg>
Both resulted in an Error.