The biggest challenges I have experienced with Security Onion are the learning curve and resource requirements, as it is not necessarily something you can install and immediately understand without networking and Linux knowledge. I actually encountered an HTTP 500 error with the management interface recently, which required troubleshooting and expanding my storage, showing me how important storage planning and system maintenance are when running Security Onion. What I would improve about Security Onion is probably the documentation around troubleshooting common issues, particularly storage management, and making the interface more approachable for new users. Having documentation of what works best would help, especially since you can have nodes or have it all built-in one as a standalone. If you use nodes, you have to have several different Security Onion instances downloaded, then have a manager and connect all of them together.
