To sucessfully render mujoco on headless machines make sure the following dependencies are installed via apt-get:
sudo apt-get --assume-yes install libxrender1 libgl1-mesa-dev libgl1-mesa-glx libglew-dev libosmesa6-dev xpra patchelf libglfw3-dev libglfw3 libglew2.0
You may perform additional steps to build mujoco-py
with gpu rendering support on a remote server without any monitor attached.