The SVG works fine in jsfiddle, which eventually led me to find https://stackoverflow.com/a/53717429 https://stackoverflow.com/a/53717429 talking about 'animati

The SVG works fine in jsfiddle, which eventually led me to find https://stackoverflow.com/a/53717429 https://stackoverflow.com/a/53717429 talking about 'animation' (which your SVG seems to mention, and I don't see a dur= property which GitHub does seem to support.)