This term mostly means “stuff I don’t agree with”. Pretty much a synonym for “Fake News”.
In other words, the term itself is bullshit. When someone calls themselves a “disinformation researcher”, it means they are hunting for stuff they don’t agree with and then trying to devalue it without any argument.
Since it is mostly fake news media that push the term disinformation, you can assume anyone using the term is probably in the business of spreading the very disinformation that they are referring to.
Box your ears. I do.