This ros2 package allows you to simualate the go2 robot in pybullet. It replicates some of the real robot topics.
For this to work you will need to have installed the unitree_ros stack (please find instructions, here). You will also need pybullet, it is recommended to install it in a conda environment:
conda create -n pybullet_ros python=3.10
conda activate pybullet_ros
conda install pybullet
After this you can do colcon build at the root of your ros workspace, and you should be able to launch this package.