expr: symbol lookup error: expr: undefined symbol: __gmpz_mul Matlab 2021A CentOS 6

On CentOS 6.10, with Rocks Cluster 6.1.1 (yes I know, old and EOL in 2020), Matlab 2021A won't start and errors with:

expr: symbol lookup error: expr: undefined symbol: __gmpz_mul
expr: symbol lookup error: expr: undefined symbol: __gmpz_mul
/export/apps/MATLAB/R2021a/bin/glnxa64/MATLAB: /opt/glibc-2.14/lib/libc.so.6: version `GLIBC_2.16' not found (required by /export/apps/MATLAB/R2021a/bin/glnxa64/../../sys/os/glnxa64/libstdc++.so.6)
/export/apps/MATLAB/R2021a/bin/glnxa64/MATLAB

2020A works fine. I've tried setting

LD_LIBRARY_PATH

to include

~//MATLAB/R2021a/sys/os/glnxa64

No luck.

strings /usr/lib/libstdc++.so.6 | grep CXXABI
CXXABI_1.3
CXXABI_1.3.1
CXXABI_1.3.2
CXXABI_1.3.3

GLIBC 2.12 is the default and I was able to get 2.14 installed in /opt but 2.17 causes all command to error out with:

error while loading shared libraries: __vdso_time: invalid mode for dlopen(): Invalid argument

Is upgrading Rocks/CentOS our only option?