To give some concrete examples, some topics where the conventional wisdom can be very inaccurate are, for example, wars and revolutions that have significant ideological bearing (like e.g. the world wars, or the French, American, or 1848 revolutions), and the evaluations of the historical performance of various systems of governance.

For some general contrarianism, I second the Moldbug recommendation. Be warned, however, that his writing features some spectacularly good insight but also some serious blind spots, so caveat lector. Generally, worthwhile contrarian sources tend to be good on some particulars but bad on others, so it's not like you can get a fully accurate opinion on any given topic from a single contrarian author.

Google "Mencius Moldbug", "Unqualified Reservations". Read until you get bored.

Alternatively read Thomas Carlyle, (long dead historian) or actual primary documents. The TIME magazine archives are pretty cool for this, as is Google Books.