That specific submission looks to have stemmed from a mutual network as the domain hasn’t been mentioned anywhere on the web outside of Hacker News.
There’s a lot of stuff out there for sure, I would imagine lots of high-potential stories for HN specifically that simply haven’t yet been discovered.
Many developers have their own homepages and they will post their own stuff and sometimes link to other sites. Groups, Discord and Slack and others are full of interesting resources, too. Mastodon has an Explore feature where you can catch some good stories.
It’s all about organising the links you find and then slowly build a network of sites you can visit to learn new things but also find new links.
Newsletters can also lead to interesting projects that never make it to HN.