What platforms to choose to market my startup, other than producthunt :)

It depends on your target market. I'll give you a few examples: If you're making a dev tool, there is Twitter, Reddit groups, Discord servers, remote events where you can do some networking and you can also engage in local dev meetups. If you're making a tool for product managers, there are plenty of Slack channels like Mind the Product, Product-led Alliance and The Product Folks. The key is knowing your target persona. What she does? Where she goes? What events she assists to? In what digital communities she participates?

Go for Twitter! Slack channels, PH communities on Reddit, WhatsApp and telegram! You can also reach out to people on LinkedIn. It's just simple steps done repeatedly for awesome results!!