I already posted this somewhere else in the forum, but here it is just in case:
I modified the spine-sfml runtime to use SDL2 instead of SFML using the new long-sought geometry render API (i.e. SDL_RenderGeometry).
It's similar to what GerogeChong did four years ago but with no OpenGL, only straight SDL.
It's also similar to a proof of concept rmg-nik did a few months ago.
I'm sticking as closely as possible to the original spine-sfml implementation. I'd say more than 70% of the code matches on a file compare. I'm providing spine-c and spine-cpp versions as well as working examples (matching the spine-sfml folders).
Come and get it: https://github.com/royalstream/spine-sdl