Ultimate Steve

Okay, you have got to hear this...

https://en.wikipedia.org/wiki/Diego_Marín_Aguilera

First off, the authenticity of this story cannot be completely validated, but several important organizations regard it as at least partially true, including the American Institute of Aeronautics and Astronautics (who credit this guy with a flight of 360 meters). This was not well reported on as it happened in a small Spanish community.

So this guy, Diego Marin, was an inventor in his small town, and he wanted to build a flying machine. He most likely did not know of DaVinci or any other flight pioneers, but he studied birds for a while and came up with, depending on which source you go by, a glider or an ornithopper (wing flapping flying machine). On May 15, 1793, he got a bunch of people to get his machine to the top of a nearby castle tower, and once the wind was right, he launched. Maybe partially due to the wing flapping, but most likely mostly due to the wind conditions, his machine reportedly rose ~6 meters in the air before beginning a descent (it was at least somewhat controllable by most accounts) before one of the metal parts broke and caused the thing to gently crash, having flown ~320 meters depending on the account. The machine was still in good condition, and they were going to fix it, but the village found out and destroyed it and made fun of him, breaking his will to continue, contributing to his early death four years later.

While the story is a bit dubious, many high profile organizations say that there is some truth to it.

This is a semi-successful manned glider test less than a decade after the first manned hot air balloon flight, and the next successful glider tests wouldn't be claimed for decades, I believe. There were a few before Lilienthal but he's the only one people really hear about.

And if it incorporated wing flapping and wasn't just a glider, then it was an unsuccessful test of a powered heavier than air craft, probably one of the most notable and early examples seeing as it glided somewhat successfully.