When filing one's tax in the United States while having a French brokerage account, what is an efficient way to efficiently know which portion of the dividends are qualified dividends? Is it possible to obtain an 1099-DIV form or some equivalent from the French broker? Or perhaps there exists some websites where one can input a ticker symbol+stock exchange and see whether their dividends are qualified?
what is an efficient way to efficiently know which portion of the dividends are qualified dividends?
You are looking for the correct way to determine it, which might not be efficient.
It is unlikely that the foreign broker will issue a 1099, because that would require them to keep up with changes in US tax code.
The complicating aspect is that that if a dividend is qualified, depends on when you owned it. So that would have to be evaluated for each quarterly dividend.
You may be looking for professional advice for this year to see what information is needed to correctly calculate the different types of income. Then doing it yourself next year.