Android has a useful, simple audio recording application built-in since Android 7.
- an audio recorder for little money (£€30-40).
- a Galaxy Samsung SIII, S4, S5 with the default recorder app from lineageos
- TP8 Telephone Pick-Up to record interviews done via mobile (software solutions are flaky or proprietary)
Audio recorder on GNU/Linux
To record a videoconference https://obsproject.com/
- adb pull /sdcard/Music/SoundRecords /tmp
- ffmpeg -i SoundRecord-2018-03-29-12-36-18.wav -vn -ar 44100 -ac 2 -ab 192k -f mp3 interview.mp3
- chromium http://otranscribe.com/
If the volume of the recording is too low, it can be amplified with:
ffmpeg -i interview.mp3 -filter:a "volume=5.0" amplified.mp3