LinkedIn is arguably the most powerful platform for professional networking and job searching. Its search functionality supports linkedin boolean search for jobs very well. You can use operators in the search bar for 'Jobs', 'People', and 'Companies'.

Finding Specific Job Titles: "Product Manager" AND (SaaS OR "Software as a Service")
Targeting Hiring Managers: Use the 'People' search: (Hiring OR Talent OR Recruiter) AND (Manager OR Director) AND "Company Name" AND (Product OR Engineering). This is a fantastic way to boolean search to find hiring managers directly.
Discovering Hidden Opportunities: Search for job descriptions that might not have a formal title yet: (building OR launching OR scaling) AND (startup OR early-stage) AND (marketing OR sales)