Directly reaching out to companies for job, is it a good idea?

In the process of finding a new job in a niche tech industry. There are few companies that I am interested to work for but none of them have posted any jobs.

They are all relatively small companies with 10-20 employees, will it be a good idea to reach out to the CEO directly via LinkedIn / cold email?

Have anyone successfully landed a job doing it this way? What’s your strategy and did you straight out asking for a job or just simply expressing that you are interested working with them?

Thanks guys

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