As the channel decoder of the simulator is implemented in C++ and compiled to .Mex files, we offer already compiled ones for 64-bit Microsoft Windows in the simulator download page. These files are platform-specific and need to be recompiled if your operating system and/or architecture differ.
With the current Matlab(2019a) supported GCC compiler still being 6.3.x, which isn’t present in Ubuntu’s standard package repository anymore, it can get a bit tedious to install the right compiler version, depending on your OS distribution and its version.
For those of you inconvenienced by this fact:
Successful compilation of the .Mex files with a newer GCC version is possible, Matlab will give out an incompatibility warning though.
Tested on Ubuntu 19.04 & 18.04, 64-bit with GCC v-8.3.0.
If the problem persists on different Linux distributions, one can try installing GCC v-6.3.x from private repositories, albeit with some OS-version support issues.