Check the communities, like reddit, telegram/whatsapp groups, HN, etc. Again, direct communication can do wonders.
Check companies websites, most tech companies have a dedicated Careers page with all the open positions and requirements, write them a personal email and wait for the response. This can give an extra karma point, because you didn't find them on some hiring website while looking for a job, you've found this position on their website, so it already tells them something about you wanting to work there.
If you are interested in startups, you can check some Y Combinator reports/news, or look at some producthunt posts, it's a riskier bet, but if you are into that kind of a thing, can be a great path.
Hope this can be helpful, best of luck with your searches!
What's your native language?
The reason for mentioning being a non-native speaker presumably was to point out that their own experience with more "niche" job boards would be with sites which are in their native language, or which have more uptake among users of their native language, such that they can't give any specific recommendations to a native English speaker.
I'm not sure how it's not fraud to advertise a job that isn't actually vacant at the time. I guess there's no incentive to stop it since it would make the jobs numbers for the economy look like worse.
The practice is lying, though, and I'll join in the chorus of voices saying that it's terrible behavior.
You can choose specific roles too such as: backend, leadership, frontend
Hacker News who is hiring threads work as well - posting your resume or reaching out to job listings.
I have got interesting interviews at startups via https://wellfound.com/jobs .