The Open University runs a Master's program in systems thinking (which I'm currently studying). There's a free primer course called 'Mastering systems Thinking in Practice' that gives a good overview and is full of references for further reading in the field: https://www.open.edu/openlearn/science-maths-technology/mast...

There's also a developing community at https://www.systemsinnovation.network/, where there are also many (subscription) resources.

The articles, books, and guides available (free) at https://thesystemsthinker.com/ are also worth a look. This mostly pertains to system dynamics rather than any other traditions, but it's a great resource for understanding complexity.