It really depends on your product, but cold emails / DMs still works if you try enough times. Launching on product hunt, HN at least gets some eyeballs and maybe some of those eyeballs convert to people who try your product.
Product hunt is debatable. I feel like it's a platform for more established products rather than new ones. Launched once, went crazy on socials, and eventually I got 5 upvotes, which is pretty decent already for a small SaaS.