/usr/share/audacity/plug-ins/ is in audacity-data 2.0.5-1ubuntu3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/audacity/plug-ins/SilenceMarker.ny
/usr/share/audacity/plug-ins/SoundFinder.ny
/usr/share/audacity/plug-ins/StudioFadeOut.ny
/usr/share/audacity/plug-ins/adjustable-fade.ny
/usr/share/audacity/plug-ins/beat.ny
/usr/share/audacity/plug-ins/clicktrack.ny
/usr/share/audacity/plug-ins/clipfix.ny
/usr/share/audacity/plug-ins/crossfadein.ny
/usr/share/audacity/plug-ins/crossfadeout.ny
/usr/share/audacity/plug-ins/delay.ny
/usr/share/audacity/plug-ins/equalabel.ny
/usr/share/audacity/plug-ins/highpass.ny
/usr/share/audacity/plug-ins/lowpass.ny
/usr/share/audacity/plug-ins/notch.ny
/usr/share/audacity/plug-ins/pluck.ny
/usr/share/audacity/plug-ins/rissetdrum.ny
/usr/share/audacity/plug-ins/sample-data-export.ny
/usr/share/audacity/plug-ins/tremolo.ny
/usr/share/audacity/plug-ins/vocalremover.ny
/usr/share/audacity/plug-ins/vocoder.ny