What are the rules on the types of files Cloudflare Pages can host? I've got my static site (a simple blog, built with Jekyll). Every post also has audio narration – a small audio recording of me reading the post. My Jekyll build spits out an RSS feed which I can share as a podcast, if I wanted to. At the moment, the audio files are hosted on Cloudflare R2. Is there anything to stop me bundling everything together, uploading it all to Cloudflare Pages, and having Cloudflare Pages host the lot?

It should be fine. Pages should be able to host any files that have standard MIME-types/File extensions. Though note that if you are hosting a considerable amount of audio files on your site, I would recommend keeping them on R2, as Pages is meant more as a site host, rather than a media host.