Ooh, they moved to stretch. That was faster than I expected.
That’s the libtool versioning. It tries to reflect the API compatibility of the library.
I just noticed that the renderers don’t pass the SDL_RENDER_ACCELERATED request to the backend, so you can get the Mesa software renderer, too. The “no matching render driver” is because of the GL library path issues in SDL. If you want to test your self-compiled SDL2, set the SDL_VIDEO_GL_DRIVER environment variable to the name of the EGL library X11 is using. That’s probably libEGL.so.1 on your system.