MacOS Microphone Permission
MacOS requires any application that wants to use the microphone to show a permission dialog.
Since Minecraft itself doesn't need the microphone, we are not able to request access for it. However some launchers add the ability to ask for microphone permission.
In order to use the voice chat on MacOS, you need to use Prism Launcher.
For Advanced Users (WIP)
If you are experienced with MacOS, you can do the following steps to get other launchers to request microphone permissions.
We do not provide support for issues with your microphone permissions if you are not using a recommended launcher.