Stream audio from only one app

1.Run Install-Module -Name AudioDeviceCmdlets -Scope CurrentUser in powershell. Pre-set the app's audio to Steam Streming Speakers in Setting>Volume>Volume Mixer. Uncheck Keep virtual sink as default and Auto capture current sink in Apollo, uncheck Play host sound in Moonlight/Artemis.

2.Use Get-AudioDevice -List to View the audio devices on the system, note the index of your Default Speaker. Not Steam Streming Speakers.

3.Add powershell -WindowStyle Hidden Start-Sleep -Milliseconds 10000; Set-AudioDevice -Index 4 (For example) into Applications>Detached Commands. The Milliseconds depends on the time your streaming launched,the number after -Index is what you noted.

4.Enjoy.

(Origin: https://github.com/ClassicOldSong/Apollo/discussions/111#discussioncomment-11284066)