There's a great list of awesome resources from high-authority sites for keyword research.
If I may add something, a quick solution to SEO keyword research is to reverse engineer your competitors.
Assuming that you have targeted a sub-niche, target your top competitors there.
These competitors almost always appear in search results regardless of the keywords you type in.
Find your competitors, enter their domains into paid SEO tools like Semrush or Ahrefs, and filter the organic keywords their content ranks for based on difficulty and monthly search volume.
Once you have a filtered list of keywords, enter each keyword manually into Google.
I cannot emphasize this enough: put yourself in the shoes of your target audience and ask yourself if this content delivers on the intent behind the keywords.
Usually, you can tell the intent of the keyword depending on the consensus you get from the search results because that's an indication of how Google reads the intent behind your target keyword.
Once you have a clear understanding of what the intent is, you can get information from the top results.
The key is to come up with more comprehensive content than your competitors.
In other words, a searcher would only have to go to your post to get all the information they would have to get by going through several sites.
Do you understand how this works?
Next is to make sure that your stuff is easier to read.
Use hemingwayapp.com and make sure your text is easy to read.
It also helps that your text is scannable, using many headings with each heading in active voice.
If possible, use diagrams, videos, and pictures.
Whatever the case, do what you must to immediately stand out from your competitors.
I'm a big fan of long-form content, but word count length is not enough.
You have to pack a lot of value into each post.
This is how you will blow away the competition, and the fastest way to do it is to do keyword research through reverse engineering.
