You have to scan all possible non-leftist sources, including those that include quite a bit of hyperbole and raving. Then you have to try to put the puzzle pieces together and make some guesses.
This author seems a little late to the game.
It really applies to both right and left sources. Both have their bias. The left spouts leftist propaganda and buries the truth in a manner that would make Pravda jealous. The right tends to report from extremely unreliable sources and sometimes pure nutcases. It's the individuals task to glean the truth and filter the lies and misinformation.
Sadly, it was our own government and media who drove people to alternate sources to find the truth. In many cases, what they found was state sponsored disinformation and nutcase bloggers, youtubers and tweeters. And much of gets posted right here on FR.