Finding low competition long tail keywords starts with choosing sources that reflect real demand and realistic ranking potential. The best approach depends on whether your site already has search data.
If you have an existing site with impressions and clicks in Google Search Console, there is arguably no better place to start. Search Console shows queries you already appear for, which means they are often within your realm of topical authority. Filter your query report using regex to surface longer phrases. For example, use (\b\w+\b\s){7,} to isolate queries that are 7 words or longer, then comb through them for terms where you are not already ranking on page 1 or 2. These are often strong content opportunities that are closely related to what you already cover, making them easier wins than starting from scratch.
You can also use third party tools like Semrush or Ahrefs to find long tail keywords by sorting for low keyword difficulty and relevant intent. Just make sure to cross reference everything with the actual SERPs. Difficulty scores and tool metrics can be inconsistent, and Google data will always be more trustworthy than estimates.