flutter_svg/example/assets/simple/linear_gradient_xlink.svg

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 94.4 94.4">
  <defs>
    <linearGradient id="a">
      <stop offset="0" stop-color="#0f12cb"/>
      <stop offset="1" stop-color="#fded3a"/>
    </linearGradient>
    <linearGradient id="b" x1="-157.994" x2="-9.071" y1="122.753" y2="122.753" gradientUnits="userSpaceOnUse" xlink:href="#a"/>
  </defs>
  <circle cx="-83.533" cy="122.753" r="74.461" fill="url(#b)" transform="matrix(.63388 0 0 .63388 100.15 -30.611)"/>
</svg>