While I can’t provide or help you find a "Stereo Tool" license key (as those are tied to specific user purchases), I can certainly write an essay about the software's role in the audio industry and the importance of supporting its development.
Restores clipped/distorted audio and adds "Natural Dynamics" to percussion. Delossifier (~€130): stereo tool license key
Breakaway Broadcast Processor (legacy free version) or Butt (Broadcast Using This Tool) combined with LADSPA plugins on Linux can provide basic loudness processing. However, none rival Stereo Tool's clipper. While I can’t provide or help you find