What do we actually know about modern disinformation?

This is an intentionally broad question with a lot of different angles. It's also a question that's naturally hard to get solid grounding on now that nearly everything gets painted as false, misleading, or disingenuous by at least someone.

Normally in my ask threads I throw out a lot of potential talking points, but in this case I want to leave the question open, for people to take it in whichever direction they wish: What do we actually know about modern disinformation, especially related to (but not limited to) online spaces? What are some real, genuine takeaways we can hang our hats on?

Also, a point of clarity: disinformation here does NOT strictly refer to high-level government propaganda and can include something as low-level as, say, an influencer not disclosing product sponsorship to their followers. I'm interested in distributed falsehoods of any caliber.