At the beginning, my son also used an adapter with an AKG wired headset. We had to change the adapter twice, which is why he let himself be persuaded to try a UGREEN TWS Bluetooth headset. After a few days of mistrust, he asked if he could keep the headset. He also reported back that not only was the sound quality very pleasant to listen to, but also that his colleagues had noticed how clear his voice was lately. Meanwhile, my model is no longer available, there are new TWS models. And there are also USB-C models, wired. See: https://ugreen.de.aliexpress.com/store...

I haven't found anything good either, or I use a Bluetooth headset.
But I find it strange that it's not good with a landline. Maybe the USB-C adapter can't handle a certain audio codec?