USB-C to 3.5mm adapter doesn’t work after iPadOS 14 update

I have an iPad Pro 2020 12.9in. A few months ago, I ordered an "Apple iPad Pro 12.9in 4th Type-C Aux 3.5mm Audio Headphone Adapter" from hedocell.com (https://www.hedocell.com/Tablet/Apple/iPad-Pro-12-9in-4th/Audio-Adapters/Type-C-Aux-3.5mm-Audio-Headphone-Adapter-Black.html), so that I can plug in an analog audio headset. The adapter has worked great until I recently upgraded my iPad to iPadOS 14, and now the adapter does not work properly anymore.

The iPad recognizes when the adapter is plugged in. The builtin speaker stops playback, setting volume displays a headphone icon, I can choose the headset for Airplay, etc. But there is simply no audio actually played out to my headset (which works fine with other devices).

My headset has a button on its cord that pauses/resumes media playback when clicked, that feature works fine on other devices, and used to work fine on the iPad prior to the update, but after the update it no longer works, either. 

Searching around, I’ve seen a few mentions of this problem with similar adapters. Is this a known issue that such adapters do not work with iPadOS 14? Is there a way to make it work again? Preferably without switching to a Bluetooth headset.

I just now updated my iPad to iPadOS 14.2, but the same problem still happens.