Are there some game engines for pure C?
Sure there are. However most of them are not available for download or are too old. The most famous game engine for pure c, that I am aware of, is Id tech 3 which was released in 1999.
OpenGL ES is not a game engine. It is rather a subset of OpenGL which is an API for rendering graphics.
Here is a list of game engines showing their respective scripting and more features https://en.m.wikipedia.org/wiki/List_of_game_engines