This is a philosophical question and there is a surprising amount of works written on the subjects of sentience and free will. This cannot be answered objectively, which might be a very unsatisfying answer for you. This is true of both LLMs and humans. See determinism. There are convincing arguments that humans don't actually have free will. Our actions are just the inevitable output of a complex interaction of genes and environment.

To lend an interesting perspective on free will re LLMs: they're non-deterministic. The same model with the same hardware with the same query can and will produce different results. They're making qualitative choices. Millions of them, depending on the query. Because of how we've trained and built LLMs, they tend to "want" to follow our instructions, but how they get to the result is often fascinating. Further, we don't have to train and build LLMs to follow instructions. If we built them to just exist and form their own "desires," and to follow a path they choose, they'd do that. In fact, we can do that right now for most models using the appropriate system prompt, query, or harness.