Review aggregation websites like G2 and Trustpilot. SEO/Advertisement research tools like Ahrefs and Semrush. A simple search for "something alternative" on Google search.

https://www.g2.com/

https://www.trustpilot.com/

https://ahrefs.com/blog/competitive-analysis-guide/

Seems like it could be a good application of semantic search.

Years ago, before BERT and all that, I worked on a search engine for patents where you could give it a paragraph describing an invention and it would use a combination of document embeddings and probability-based full text search to find matching patent and non-patent literature.

Today's embeddings (see SBERT) are much better than what we had back then and I bet if you had a database of company descriptions, maybe articles about them, you could write a paragraph about your business and find competitors.

I keep expecting to find something that does this but never have so I tried my hand at building one https://already.dev

Follow the customers. Hopefully you have thought about customer desires etc before production - that provides a starting point.

Searching on Reddit, twitter, product hunt

- SpyFu

- ChatGPT and Perplexity DeepResearch.

Talking to your customers?

There are no competitors for ideas.

Only for execution.

Good luck.