There's an error in exporting to PDF from Indesign when you have an SVG placed, and that SVG contains an smlns:sxlink attribute - this makes it impossible to create the PDF (and thus, use the software to create your document).

The 'PDF export failed' error message doesn't give any info on how to fix the issue. And the default .svg export from Illustrator adds in that .svg attribute... so I create my graphics in Illustrator... but then they prevent my InDesign file from creating documents! Not great.

If you remove the part that says:
xmlns:xlink="http://www.w3.org/1999/xlink"

Then the opening tag will look like this:
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 693.21 430.88">

Then resave the SVG, after which there’s no issue with exporting the PDF from Indesign.

There’s something about that property on the svg that the INDD export function doesn’t like, and throws up an error on.

There’s obviously been some kind of change in default export values when Adobe Illustrator is creating SVG files; because this wasn’t a problem in the past, and I haven’t custom-edited the svgs until I thought to try it just now.