Dirty trick to be able to use the matlab GUI to install update 3:
bert@Dell7577Linux:/usr/local/MATLAB$ sudo chown -R bert R2018b/
bert@Dell7577Linux:/usr/local/MATLAB$ sudo chgrp -R bert R2018b/
and after installation:
bert@Dell7577Linux:/usr/local/MATLAB$ sudo chgrp -R root R2018b/
bert@Dell7577Linux:/usr/local/MATLAB$ sudo chown -R root R2018b/