Is This A Rare Hungarian Note Or A Fantasy?

The quality of the printing tells me it is not genuine.

Have you checked the Exonumia section of Numista?
https://en.numista.com/catalogue/in...?ct=exonumia

There may be something like it there. It could be a souvenir, a voucher or a specimen that was never issued (by a provisional government? Why not?) Its production looks rather crude/basic however to be a printer's proof note. But I would not declare emphatically that it is not legit unless I could inspect it in person.

There are countless paper & token "rarities" out there that nobody wants but are described as "must haves" on planet ebay (& other platforms). Just b/c somebody has described "X" as "Z" doesn't necessarily mean it is whatever they've claimed (ie special).

My position is, if in doubt, take a pass.