Recently I bought a new Macbook Pro running Mojave. I found myself unable to get the microphone to work for the in-game voice chat using the ‘v’ key.
The closest solution I could find was mentioned in this article:
This article was oriented towards League of Legends, so I had to modify the commands used to enable this for steam.
You still have to reboot the Mac while holding Command + R during start up.
In the recovery mode you’ll have to use the menu to run the Terminal, and
After this is completed, reboot the computer.
sudo sqlite3 ~/Library/Application\ Support/com.apple.TCC/TCC.db "INSERT or REPLACE INTO access VALUES('kTCCServiceMicrophone','com.valvesoftware.steam',0,1,1,NULL,NULL,NULL,'UNUSED',NULL,0,1551892126);" /usr/libexec/PlistBuddy -c "Add NSMicrophoneUsageDescription string" /Applications/Steam.app/Contents/Info.plist /usr/libexec/PlistBuddy -c "Set :NSMicrophoneUsageDescription Using voice chat" /Applications/Steam.app/Contents/Info.plist
Reboot into recovery mode again, open the Terminal and run
csrutil enable. Restart once again.
After doing this, the Rust game was able to transmit my voice from the mic.