Multiband compression & limiting , like ToneBooster’s broadcast plugin
Good News: ToneBooster’s broadcast v3 plugin is free.
Now the bad news: v3 is not VST3, so it won’t work in real-time in Audacity3,
(but is real-time in Audcaity2).
More free multi-band compressors … FREE Multiband Compressor VST Plugins - Bedroom Producers Blog