I have a fresh install of MEEP (the FDTD package) in a Conda environment, on a fresh install of elementaryOS. I'm attempting to run the "Visualizing 3D Structures" example code found here. I've installed both both pymeep and pymeep-extras, as well as scikit-image and vispy (dependencies for the example code).
Running python3 visualizing_3d_structures.py within the Conda environment yields the error libEGL warning: DRI2: failed to authenticate, and no graphical display appears. A simple Google search reveals a number of StackExchange posts (with various, at times contradictory advice) relating to a similar issue specific to Raspbian. none of which seems relevant here, unfortunately.
This could happen if there isn't a backend (software graphic device) installed in the environment, but there is a libEGL installed at the system-level (EGL is one of the backends for which MEEP will search).
The recommended backend for MEEP is PyQt, so installing that should be sufficient get it working:
conda install -c conda-forge pyqt
That works for me. However, the tutorial directly recommends mayavi. This will also install pyqt, but obviously has extra stuff as well. So, if you want to strictly follow the tutorial, then run
conda install -c conda-forge mayavi
I verified that also gets it working.