I hope this can be a tracking issue for supporting MuJoCo 2.1.1, which was just released few hours ago. There are some incompatible changes, so the python binding mujoco-py also needs to catch up those changes.

Required changes include:

• The path to the shared library has changed to lib/libmujoco.so (previously bin/libmujoco210.so)
• Perhaps expected installation paths might be $HOME/.mujoco/mujoco211 per the convention. However, this naming convention is because of the directory name in the archive, which is mujoco210; the new release 2.1.1 no longer uses this convention. Therefore mujoco installation path might also need to be changed (discussion/opinion needed).
• For MacOS, MuJoCo is now provided as a Framework bundle, so it is no longer expected to have a load path under $HOME/.mujoco. The standard MuJoCo installation path on MacOS systems seems undetermined yet, so we might need to wait a bit more to hear from DeepMind.

In addition, the builder script also needs to be updated because currently GCC only up to v9 is supported: #605.

I already managed to make mujoco-py work locally on my M1 machines, so creating and submitting a patch will be quite straightforward but we'll have to make a few decisions.