The ‘free’ version of NotebookLM has a series of limitations on sharing and on the number of sources.
The ‘try your own’ the systems here are set to work under these constraints. It is limited to 50 authors (or Voices) the full list of which is here. It has meant I have had to cull key authors such as Christopher Alexander for his insight into Complexity and David L Abel for his thinking of the ontological/epistemic gap (between what we think and what the physical world can do).
Sharing of NotebookLMs is possible between Personal Accounts either to Enterprise or Education Accounts but NOT from Enterprise or Education Accounts to Personal. This is so stupid and damaging - akin to limiting books to a select few.
There is a significant gotcha that you need to be aware of NotebookLM is probabilistic not deterministic, this means it may not produce the same answer twice as explained here. If person A uses this system to probe some aspect even with the same prompts person B may see a different response. It is a Research-Project to see if the expected difference are different in essence (fatal), detail (annoying) or style (trivial).
Alternatively: You can download the source material and upload them to your own NotebookLM system, for each of the aspects of Systems Thinking - available at the downloads index