I think this is the last known good posting for De Esser.
https://forum.audacityteam.org/t/updated-de-clicker-and-new-de-esser-for-speech/34283/1
Go > Applications > Audacity Plugins
Dump the .ny in that folder. Restart Audacity. Effect > Add Remove Plugins > DeEsser.
That page has an extensive tutorial on how to use it. I only used it in the default values and I never got good at it.
Who shot your guest? Did they by any chance use a USB microphone and then apply very stern noise reduction? Did they save a WAV of the shoot before they applied any corrections?
Koz