Yeah, the commercial plugins are also an interesting feature. The engineering focus of the platform makes it easier to do commercial development.

Octave has "toolboxes", they are called packages: https://octave.sourceforge.io/

I don't have extensive experience with Matlab's toolboxes, but my impression is that most toolboxes without graphical interface (e.g., optimization, signal processing) have an octave equivalent with the same function names and mostly compatible. What is missing are the "gui" toolkits like simulink, the circuit stuff, etc.