The new KDE Plasma releases require a slight change in your svg files, if you have a radiant gradient (no problems instead with the linear ones).
You have to specify the radialGradient cx, cy and r, like in the following example:
<?xml version="1.0" standalone="no"?>
<svg viewBox="0 0 22 22" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<radialGradient id="gradient" cx="0.50" cy="0.50" r="0.45">
<stop offset="0%" stop-color="#fbfbf0"></stop>
<stop offset="80%" stop-color="#bc5a1f"></stop>
</radialGradient>
</defs>
<g>
<path fill="url(#gradient)" d="M11 .008l3.4 6.888L22 8l-5.5 5.361 1.298 7.57L11 17.357l-6.798 3.574 1.298-7.57L0 8l7.6-1.104z" />
</g>
</svg>Because a svg with this other following code won’t work (will be invisible)
<?xml version="1.0" standalone="no"?>
<svg viewBox="0 0 22 22" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<radialGradient id="gradient">
<stop offset="0%" stop-color="#fbfbf0"></stop>
<stop offset="80%" stop-color="#bc5a1f"></stop>
</radialGradient>
</defs>
<g>
<path fill="url(#gradient)" d="M11 .008l3.4 6.888L22 8l-5.5 5.361 1.298 7.57L11 17.357l-6.798 3.574 1.298-7.57L0 8l7.6-1.104z" />
</g>
</svg>