As I understand it, there is not a single clear definition of what is meant when we say that something is true. The Stanford Encyclopedia of Philosophy, seems to list at least five major schools of thought on the subject.[1]

So, given "This sentence is false" it seems to me that there must be assumptions behind it that cause us to perceive it as a paradox.

Interested in your thoughts, if you wish to say more.

[1] https://plato.stanford.edu/entries/truth/