on that page https://github.com/clearlinux/clear-linux-documentation/blob/master/source/tutorials/nvidia.rst
that section
Create a systemd service unit to overwrite the |CL| provided :file:libGL.so.1 files with a symlink to the NVIDIA copies.
has wrong path?
ExecStart=/usr/bin/ln -sfv /opt/nvidia/lib/libGL.so.1 /usr/lib/libGL.so.1
but should be /usr/lib64/libGL.so.1?