I didn't know that the <a> element had a download attribute, nor that it could rename the file on download for you e.g:
<a href="/files/ugly-file-name.xyz" download="nice-file-name.xyz">download</a>
On top of which, I didn't know that redirects using Netlify's _redirects file (which IĀ do know about š) would allow for same-domain downloads (which the download attribute requires):
/download/* https://clearleft-audio.s3.amazonaws.com/podcast/:splat 200
Basically, this whole article is a TIL.