Mfix-21.4 & RHEL 7.5 with X11 starts and fails to open GLEW could not be initialized: Missing GL version

Please try to get glxgears to run before attempting anything else that uses OpenGL. We can only provide limited support in debugging your platform issues.

A quick Google search for libGL error: failed to load driver: swrast turns up this thread:

How can i deal with 'libGL error: failed to load driver: swrast.' · Issue #509 · openai/gym · GitHub

which suggests installing the mesa-utils and libgl1-mesa-glx packages.

It also suggests testing by using the environment LIBGL_DEBUG:

LIBGL_DEBUG=verbose glxinfo