Yup. That’s your issue. Disney+ outputting Dolby 5.1 and your speakers are stereo.

That's not what the link says. In fact it is specifically saying it should be working in stereo but tdolby surround has missing channels.

Well it's still their fault for not making sure their audio works on a normal, non-surround setup

Also worth noting that we switched the audio track to Spanish and you can hear it just fine.