How can I enable custom SVG fonts for Image Viewer (Eye of Gnome)?

Question

I have some SVG files with custom fonts. I can open them and fonts look nice in Firefox, but the font is not properly displayed in Eye of Gnome (Image Viewer) application.

Why is this so, and how can I fix it?

I am using GNOME Image Viewer 3.38.0.

This is an example SVG header:

<svg viewBox="0 0 1297 1600" version="1.1" preserveAspectRatio="xMinYMin meet" text-rendering="geometricPrecision" class="pq" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
  <style type="text/css">
    text{
      white-space: pre;
      font-size: 16px;
      font-weight: normal;
      font-style: normal;
      stroke-width: 0;
      fill: none;
      unicode-bidi: bidi-override
    }
    @font-face{
      font-family: "pf4";
      src: url("data:application/font-woff;charset=utf-8;base64,d09GRk9UVE8AAAZsAAkAAAAAC...") format("woff");
    }
    @font-face{
      font-family: "pf6";
      src: url("data:application/font-woff;charset=utf-8;base64,d09GRk9UVE8AAAeMAAkAAAAAC...") format("woff");
    }
    .p1 .f1{
      font-family: "pf4",sans-serif;
      line-height: 1
    }
    .p1 .f2{
      font-family: "pf6",sans-serif;
      line-height: 1
    }
  </style>
</defs>
...