Reporting correct Qualified Dividend - if an amount is subtracted

A certain broker, in the tax info guide shows in line 1b it "will not determine if applicable holding periods have been met"

So, according to instructions in 2020 1040 "Dividends you received on any share of stock that you held for less than 61 days during the 121-day period that began 60 days before the ex-dividend date. The ex-dividend date is the first date following the declaration of a divi-dend on which the purchaser of a stock isn’t entitled to receive the next dividend payment. When counting the number of days you held the stock, include the day you disposed of the stock but not the day you acquired it"

When I look up the dividend history (eg https://www.nasdaq.com/market-activity/stocks/alsn/dividend-history for example), why are these dates not listed? If everyone looks them up to see which are actually usable for the qualified dividends line? (I wrote a js script to calculate such a date on https://gist.github.com/programmin1/28ac27d95fa31c4a1e823a377f2e0867, at least it can be calculated in javascript real quickly upon clicking that ex-dividend… or using any number of other online date diff tools.)

Second, what is an appropriate way to report subtraction of such a dividend if short sold regarding holding period for the dividend? Looking at the history buy/sell of such a stock and just crossing off the reporting 1099 long sheet, and/or tallying a separate sheet with a subtraction of the sum of each (# stocks) * (cash amount) from Nasdaq for any that you find not applicable for the qualified holding as reported in their 1099-DIV?