Uma solução poderia ser usar Pipelight:
Aqui, como instalar o Pipelight no Ubuntu: link
sudo add-apt-repository ppa:pipelight/stable
sudo apt-get update
sudo apt-get install --install-recommends pipelight-multi
sudo pipelight-plugin --update
Veja como ativar o plug-in do Unity Web Player: link
#!/bin/bash
#FDS-Team: Pipelight Project
#Tomasz Zackiewicz, Pipelight.sh
#update the checksum of Unity3D Web Player
sudo pipelight-plugin --update
#for Firefox, clear the plugin cache
sudo pipelight-plugin --create-mozilla-plugins
#enabling Unity3D Web Player
sudo pipelight-plugin --enable unity3d