So I checked the Bing Webmaster Tools. URL Inspection says "Discovered but not crawled - The inspected URL is known to Bing but has some issues which are preventing indexation. We recommend you to follow Bing Webmaster Guidelines to increase your chances of indexation."
That's quite unhelpful. What's more, when I open the "Live URL" tab, it says, in green: "URL can be indexed by Bing."
It's a simple static Hugo site hosted on Cloudflare R2 (DNS mapped directly to bucket). https://pagespeed.web.dev gives it a score of 100 in every category.
Anyone else had something like this happen?