Doing the git pull, autoreconf, configure, make, then make install worked.
For the libstdc++.so.6 and MPI errors, I had to point to both of them in LD_PRELOAD. This is what worked for me:
LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libstdc++.so.6:"${ISSM_DIR}/externalpackages/petsc/install/lib/libmpi.so:${ISSM_DIR}/externalpackages/petsc/install/lib/libmpifort.so" matlab -softwareopengl
I had to add the -softwareopengl to deal with the "Low Level Graphics" error.
Thanks!