The honest founder post. "I make [product category]. Here's what I got wrong in my first version and what changed." This works because it's disclosed, specific, and not selling anything directly. It builds the kind of long-term credibility that pays off over months, not the post itself.
The genuinely useful answer. Someone asks "best X for Y use case" in a relevant subreddit. A real answer: "I've tried three options in this category. [Competitor] is better for [specific use case], but if you need [specific requirement], [your product, disclosed] handles it better because [specific reason]." Naming a competitor fairly, and disclosing your stake, is what separates this from being removed as spam.
The correction or clarification. If there's an existing thread with outdated or inaccurate information about your category or brand, a specific, sourced correction, not a sales pitch, is often welcomed, especially in a subreddit whose whole culture is built around calling out inaccurate claims.
What doesn't work, reliably: a first post to a subreddit that's a product link, an AI-generated-sounding testimonial, or a reply to an unrelated thread that pivots into a pitch. All three get removed quickly and, worse, get remembered.