During the stakeholder and user interviews, they might mention a few competitors. The stakeholders probably will tell you the ones they consider as competitors from a business point of view. The users might mention the same competitors and likely other ones that they consider deliver the same or similar solutions. It is a good moment to also understand how they use the competitor and why they consider it as a substitute solution, what is best and worse if compared to your product or service. The users might mention competitors that the stakeholders didn't know exist or even don't consider as a competitor. During research you might find other ones too. It is important to analyze all of them.
Analyzing the competitors, ...