Gradient problems when going from .ai to .svg with the new Illustrator 28.4.1 before it was fine

I'm having the same issue with very simple radial gradients. I've tried rolling back to a few different 2023 versions and it's still causing the problem, so there's something bigger happening because I was able to export gradients fine last year. Seems the latest updates across the board for Creative Cloud have introduced only problems; there are issues with Photoshop and XD also (the latter is on maintenance mode so who knows if Adobe will ever fix XD.)

This may not be your issue, but Illustrator 28.4 completely changed the format of SVG files exported throught scripting. I am submitting a bug report separately because it has completely broken my workflow.

The previous format looked like this:

<?xml version="1.0" encoding="utf-8"?>
<!-- Generator: Adobe Illustrator 27.9.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
	 viewBox="0 0 500 500" style="enable-background:new 0 0 500 500;" xml:space="preserve">
<style type="text/css">
	.st0{clip-path:url(#SVGID_00000050657835777145769900000007173324349283303303_);}
	.st1{fill:#FF000D;}
	.st2{fill:#CA00D5;}
	.st3{fill:#2AEC00;}
	.st4{fill:#F0AB00;}
</style>
<g id="layer_2__x2F__extra_content">
	<g>
		<defs>
			<rect id="SVGID_1_" x="207.75" y="328.25" width="128" height="128"/>
		</defs>
		<clipPath id="SVGID_00000120556236775382720460000010520103355737100182_">
			<use xlink:href="#SVGID_1_"  style="overflow:visible;"/>
		</clipPath>
		<g id="clipped_group" style="clip-path:url(#SVGID_00000120556236775382720460000010520103355737100182_);">
			<rect id="Rectangle_x5F_smaller" x="150" y="270.5" class="st1" width="128" height="128"/>
			<rect id="Rectangle_x5F_Grandé" x="193.5" y="367" class="st2" width="40" height="40"/>
		</g>
	</g>
</g>
<g id="layer_1_200_x25_">
	<g id="group_1__x3E__group_2">
		<rect x="37.5" y="33.5" class="st3" width="116.5" height="116.5"/>
		<rect x="106.25" y="102.25" class="st4" width="116.5" height="116.5"/>
	</g>
</g>
</svg>

And the new format looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" viewBox="0 0 500 500">
  <defs>
    <style>
      .cls-1 {
        clip-path: url(#clippath);
      }

      .cls-2 {
        fill: none;
      }

      .cls-2, .cls-3, .cls-4, .cls-5, .cls-6 {
        stroke-width: 0px;
      }

      .cls-3 {
        fill: #f0ab00;
      }

      .cls-4 {
        fill: #ff000d;
      }

      .cls-5 {
        fill: #2aec00;
      }

      .cls-6 {
        fill: #ca00d5;
      }
    </style>
    <clipPath id="clippath">
      <rect class="cls-2" x="207.75" y="328.25" width="128" height="128"/>
    </clipPath>
  </defs>
  <g id="layer_2_extra_content" data-name="layer 2 / extra content">
    <g class="cls-1">
      <g id="clipped_group" data-name="clipped group">
        <rect id="Rectangle_smaller" class="cls-4" x="150" y="270.5" width="128" height="128"/>
        <rect id="Rectangle_grandé" class="cls-6" x="193.5" y="367" width="40" height="40"/>
      </g>
    </g>
  </g>
  <g id="layer_1_200_" data-name="layer 1 200%">
    <g id="group_1_group_2" data-name="group 1 &amp;gt; group 2">
      <rect class="cls-5" x="37.5" y="33.5" width="116.5" height="116.5"/>
      <rect class="cls-3" x="106.25" y="102.25" width="116.5" height="116.5"/>
    </g>
  </g>
</svg>

You can immediately tell the difference because the previous style definitions began with "st" and the new style definitions begin with "cls-".

That gradient looks like you are using a blend mode in addition to the gradient. Can you please be specific as to how that artwork has been built? SVG does not support all those blend modes and transparency stuff that Illustrator has.