You can’t reliably force mobile/tablet browsers to download the whole file before playing. They are designed to stream audio in chunks, and they will refuse playback if the server doesn’t handle Range requests correctly.

So there’s no setting on the tablet to make it “download everything first.” The only practical solution is to have your Worker forward the Range header and return the correct partial content from Backblaze. That satisfies the browser’s streaming requirements and works everywhere.

If you want, I can show the minimal change to your Worker to make audio play on tablet without breaking anything else.