Perhaps Limiter with make-up gain, (possibly applied repeatedly), but that could noticeably damage the good audio.
or AutoDuck a duplicate of the track with the original,
that could raise the volume of the quiet (dropout) sections but leave the good audio untouched.
[IMO Steve’s Dynamic Mirror plugin is easier to use than Audacity’s native AudoDuck].
If the dropouts are true mono perhaps that change (from stereo) could be used to selectively amplify them 