I found:
shlomnissan/sdl-wasm:
https://github.com/shlomnissan/sdl-wasm :
> A simple example of compiling C/SDL to WebAssembly and binding it to an HTML5 canvas.
erik-larsen/emscripten-sdl2-ogles2:
https://github.com/erik-larsen/emscripten-sdl2-ogles2 :
> C++/SDL2/OpenGLES2 samples running in the browser via Emscripten
IDK how much work there is to migrate these to SDL3?
Are there WASM compilation advantages to SDL3 vs SDL2?