Hello,
Quectel RIL supports phone calls, SMS, data connection and more. For the voice call, the module must support PCM, RIL will only send Voice Call AT commands, such as ATD and ATA, ATH. None of this has anything to do with UAC. L UAC is supported on Linux. For details, see Quectel_LTE_Standard_UAC_Application_Note_V1.0.pdf. But how to use on Android, such as you want to play the sound for the remote, or record the sound from the remote, these involve Android Audio, Android to transplant the ALSA driver, select the audio path, adapt to Android HAL, this requires the Android side, That’s RK3568 for support. Android Audio is complex.
If any other manufacturer’s 4G module supports UAC to make and receive calls on Android, Quectel will also develop this feature.