e.g. they're told that this kind of creature has some kind of psychic or pheromone-based "mate bond" that cannot be broken; but it turns out that's a popular myth that has never been scientifically substantiated, and is basically used to keep people in bad relationships (basically the equivalent of "human women are biologically submissive")

"lore" is imo too often treated like information that the author is giving the reader, and it just happens to be using the medium of diagetic (that is, 'in-story') exposition.

it's so much more interesting and dynamic to treat "lore" as information that is generated and disseminated in-story. who is telling the protagonist this information? under what historical and social circumstances was this idea formed? what political motives are there for trying to get people to believe this information? which characters would disagree with it? would the protagonist believe it, or be sceptical? does the plot bear it out, or cast doubt on it?

OK so Massive spoilers for the first Mistborn book.

Brandon Sanderson does this really well, I think.
A lot if not all the lore we're given in the first book is called into question by the end of the book and this continues on into the second book. I've got a lot of examples down below but I must insist that these are massive spoilers they will taint your enjoyment of the book since it heavily relies on these misconceptions, misunderstandings and altered histories to drive the plot.

Seriously if you want to read Mistborn go do it and do not read further.

SPOILERS AHEAD!

They've got a class divide between the slaves called Skaa and the nobles. Most nobles are taught to believe the Skaa are lesser and stupid. This is such a widely held belief that even the main characters question if it's true and they are Skaa and have fooled other nobles into believing they aren't. But it's later revealed that it's not just the Skaa being a repressed, uneducated and generally beaten down people. The Ministry actually has emotion dampening stations scattered through the slums to keep them from having any passion or strong emotions.

The Lord Rulers is an immortal that can survive burnings, decapitations and you name it because he's a "sliver of god"? Nope just a combination of magic systems that make him appear that way.

The little paragraphs at the start of each chapter are from the Lord Rulers diary that the main cast steal at the mid point of the book? No! It's the Hero's diary and his packman killed him and took his place. Which is why they don't match up personality wise and not because becoming a part god changed him.

There are only 8 standard magic powers and the 2 timey wimey magics? No again there's a 9 and the 2 time ones are separate magics and not a pair so there's another 3 undiscovered ones out there. By the start of the 2nd book the main character is doing research into them because if people missed that many how many more could there be?

There's a secret 11th magic that can kill the Lord Ruler? Nope, I think this one might be a broken telephone situation. "The 11th metal will reveal that the Lord Ruler killed the Hero" became "The 11th metal can kill him" because he was faking being the hero and wires got crossed but it is never confirmed in the books.

People using copper magic can't be detected as using magic? Nope turns out the inquisitors can still detect you. Which recontectualises the supposed betrayal the main suffered.

mistborn is an especially fun example of this because (spoilers ahoy) if the reader is paying attention, you can watch the lore change in real time, because it is being actively fucked with by an antagonist god(?)

one of the key plot points of the second book is an established prophecy about the 'Hero of the Ages.' One of the characters goes to examine the original text of the prophecy and realizes to his excitement that the description of the Hero is gender neutral! Does this mean the prophecy could actually apply to his friend, Vin, after all?!

Nope! The prophecy always used male pronouns. It was being edited on the fly to mislead the characters.