It's getting embarrassing that every other mobile and desktop OS has no problem doing this but not Ubuntu.
You can't work around the fundamental limitations of Bluetooth protocols like A2DP without cheating and using another microphone somewhere else. You can't use the headset mic when receiving high quality A2DP audio, ever, no matter how hard you try. It is a limitation of the Bluetooth standard.
When you switch the device into headset mode the quality turns to potato because it uses bidirectional audio codecs from the stone age in HFP/HSP mode with mSBC or (god help us all) CVSD.
> It’s because of the limited bandwidth in Bluetooth that it has to lower the audio quality
It's not a bandwidth limitation. According to google A2DP supports up to 728kbit/s, but SBC (the default codec) only goes up to around 300. Clearly there's enough bandwidth for mid quality input and output streams.
In the real world, you get a lot less bandwidth. In my office building I see 300-400kbit/s of real throughput. The radio also only has one transceiver, if you connect multiple devices, they have to take turns broadcasting which cuts your bandwidth roughly linearly proportional to the number of nodes.
Also remember that Bluetooth and WiFi share the same spectrum. A high power or very busy WiFi network nearby will also drop Bluetooth bandwidth. You also get a precipitous drop in bandwidth if there are other Bluetooth devices nearby, as they all have to share the same spectrum.
There's a lot of effort put into mitigating these problems, but either way the real world performance of Bluetooth is much, much lower than theoretical figures. Streaming useful audio over a link like this is not a trivial problem.
At work, I'm currently trying to cram ten separate audio streams into a Bluetooth link for reasons. We're switching to WiFi.
The aptX codec allows for CD-quality audio over Bluetooth:
* https://www.qualcomm.com/news/releases/2021/09/qualcomm-adds...
* https://en.wikipedia.org/wiki/AptX
Comparison of three in-ear monitors (IEMs):
Windows is the worst of the worst, but every Linux distro I've tried works great and actually supports every feature of Bluetooth. Unlike Windows, who only implements the barest of minimums, and about half of those features just don't work.