>early-stage detection, without needing to pay for, or wait for, training a custom ML model
This doesn't make much sense though, if you're in a hurry to get something working and don't have the data for training a custom model, you'd use the knowledge you have of the system to setup a typical statistical anomaly detector. That way you'd have the insight into the system behavior that you'd want early on, would be able to enforce all sorts of guarantees and would not have the weight and complexity of an LLM on the system's resources, rather than worrying about this LLM that has nowhere near the same info on the system.
Using an LLM for this would be like hiring a random person off the street to keep your network infrastructure working because you're in such a rush that you don't even want to document how your infra is setup, let alone wait to find someone who would know how to decipher it.