Audacity comes with has dynamic-range-compression …
https://manual.audacityteam.org/man/compressor.html
But IMO it’s too slow for speech. LevelSpeech2 is better.
Neither of those plugins work in real-time.
There are MANY free real-time compressor plugins, e.g. …
TDR Nova | Tokyo Dawn Records (complicated: multi-band)
TDR Molotok | Tokyo Dawn Records (simpler: one band)