If your college/university teaches you anything on Matlab then most likely they have Campus Wide Access license.
Which means you can use your student university email to register an account with Matlab and gain free access to use Matlab and Simulink software on your own PC/Mac computer.
After downloading the software and installing it, make sure you select all the libraries you need during the installation process.
Also make sure you are signed-in, in the software itself using your Matlab account, for the license to activate.
I have heard of SageMath, but never used it.
I have never seen people use tooling like that in industry. It could be that I am simply not interacting with companies that do, but across all the modeling I have done I have yet to see symbolic math.
The closest thing I have used to symbolic math is PyMC which is a bit of a stretch.