Requirements:
1. A Rooted device with Latest Magisk
2. ScreenCam Magisk Module (Download)
3. ScreenCam Screen Recorder (Download)
Steps to Install:
1. Download the ScreenCam Magisk Module zip file from the link above.
2. Open Magisk Manager and go to Modules.
3. Tap on + icon and browse to the zip file.
4. Tap on the zip file and it will get installed on its own.
5. Tap on Reboot.
6. After the system restarts, go to Modules tab again and check if it is installed properly.
7. Now download the Latest ScreenCam Screen Recorder from the link above. (It will redirect you to Play Store).
8. Now in ScreenCam Settings, tap on Record Audio.
9. Select Internal Audio (System app,R_Submix).
10. Then you can start recording, it will record from the internal audio instead of using your device mic.
Note: While recording you won't be able to hear the audio because the app uses Screen Cast techniques to record the internal audio.