As someone who has built event pipelines from GDELT data, I'd advise folks to not start (a GDELT project) with high expectations. Not only are there plenty of duplicates, but tagging quality is all over the place, especially for non-Western media.
I think GDELT is the best source, nothing else comes close to coverage in my opinion, it's just that all the articles it gathers revolve around world events, as opposed to all of the millions of topics of discussion and niche interests people post about.
More info: https://blog.gdeltproject.org/gdelt-translingual-translating...
(unrelated: scrolling on that page is horrible)
What are you using instead of GDELT now?
Our domain was pretty well defined, and we weren't building a real-time system, so we developed an adjudication tool and hired a few part time employees to evaluate and clean up our output.