this has been one of my biggest doubts, anyone knows about INDIE games made with C++ and OpenGL/Directx/SDL/SFML/Any library, that have pixel art graphics? Except "Shovel Knight", im talking about something like "Owlboy" graphics, beautiful pixel art

which ones? i don't find anything

All of the games that come up from the link that Jacmoe provided are indie games and have a "pixel graphics" tag. Looking a bit further at a couple of them they appear to be using pixel art.

If none of these games fit what you're asking for people to find you, why do they not fit? What are you looking for? Why is it that you have doubts about pixel art being used in indie games?

games made with C++ and OpenGL/Directx/SDL/SFML/Any library, that have pixel art graphics?

Pixel art is a graphical style. OpenGL, DirectX, SDL, and SFML all support drawing 2D graphics, and thus all "support" pixel art as a style. The "style" is handled by the textures being drawn by the artist, not by the language or library used to code the game.

I personally have used C++ and SDL, C++ and SFML, and (now) C++ and OpenGL. All of them are capable of pixel art graphics.

See Frogatto, which uses SDL for window and input management and OpenGL for graphics rendering, and has some of the most beautiful pixel art I've ever come across in any game.

See Dust: An Elysian Tale. A wonderful game made by a one man army. That feat is just freaking incredible. And I don't think he's using unity or unreal either. Unity wasn't really that popular of an engine back then. And sprites were a pain in Unreal.

and most importantly...

Ori: The lost forest. Which in my mind, is an absolutely beautiful game. They did quite a bit of cheating to get past hand making sprites. But in the end, it still uses sprites. It just cheats very well. The character sprites were actually created by orthogonality rendering 3D models. And the level was hand made.