Reducing "hollow" sound in recording

The problem sounds like reverb in the room.
The only real way to prevent that is acoustic treatment of the room, (heavy blankets, thick foam, carpet),

There are de-reverb plug-in$ to reduce reverb in post-production,
but they generate computery artefacts … https://forum.audacityteam.org/t/slight-boxy-sound-on-voice-recording/55407/6