Macbook Air 2020  Acer-ET322QR Audio not integrating
The issue that you’re running into is that you’re going from DisplayPort to HDMI (signal conversion).  Now DisplayPort as an industry standard has support for audio as does HDMI.  However, DisplayPort and HDMI are very different signals.

What makes this confusing is that we bring the term “USB-C” into the mix.  USB-C is just the physical connector type.  That port on the MBA is several signals, including DisplayPort, in one port. 

The first thing I would look at is going with an Active Adapter, not a passive one (cable) that just re-orders the pinouts to match what you need. 

As for your audio, I’ve never been a fan of integrated audio speakers in monitors and definitely not a fan of HDMI video connections in my compute environment - it’s a consumer grade AV spec that I’ve found very flaky.  I would go with a USB audio adapter (DAC) that can connect to a much better set of speakers or even audio amplifier.