But for that you really have to know who the various luminaries of the relevant fields of interest are, and kind of track their world a bit. A lot of them don't post online much because for one, they have recognized that the platform we all have here in general is designed for grosso modo memetic "learning" which happens in a native self-reinforcing projection-style loop as opposed to more fluid, open learning and knowledge production by design.
So maybe what you'd be more likely to find that's useful and cutting edge here on the web, and in more readily consumable form, is more like public project updates and data.
For this I would offer GitHub, phys.org and your locale's weather service, e.g. weather.gov. You could probably lift the world with those sites if you can readily metabolize what they've got going on.
For example, if you dig quadruped robots (I do) follow https://mobile.twitter.com/leggedrobotics/status/14838769163...
But I don't think most people really do, because that's far too much noise to parse. Most people probably want it to have passed the bullshit test (so many academic papers make fake claims now), been tested, and been wrapped up and demonstrated in a neat Python library or similar. Somewhere like this is probably the best place for that.
So, I get cutting edge information from blogs operated by tech companies. Stackoverflow also has a really good blog.
Reddit, to some extent.
Mailing lists for various open source projects.
And HN of course
In your RSS client you could tag your RSS subscriptions and create feeds like "Technology", " Politics", "Philosophy", etc.