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If you have not already done so, I would try installing and running a version of the Matlab runtime environment (which is not a full blown Matlab installation) that freesurfer was tested with.  For the 7.4.1 freesurfer release, that should be R2019b.  (Prior to that, it was R2014b - which you could try as well - but that would likely contain an even older version of glibc).

Assuming that you can write to your own installed version of freesurfer, then once you have set FREESURFER_HOME, you can try running the fs_install_mcr script included with the freesurfer distribution.  See bash shell commands below.

- R.

$ export FREESURFER_HOME=<your install path>

$ cd $FREESURFER_HOME/bin

$ sudo FREESURFER_HOME=$FREESURFER_HOME  ./fs_install_mcr  R2019b

… answer y to any installer questions ...

Then I think it should work to find the Matlab libraries by at least start off with setting,

$ export LD_LIBRARY_PATH=$FREESURFER_HOME/MCRv97/bin/glnxa64

Please make sure you have otherwise removed any references to your previous matlab 2020a environment from PATH, LD_LIBRARY_PATH, etc. 

- R.