WebGL2 also supports them! And now that Apple finally added support (like half a year ago(?)) to it, it can be fairly safely used
Apple does support WebGL2, but compute shader support is not part of that core spec. The demos[2] certainly don't work in Safari in my quick test.
[1]: https://registry.khronos.org/webgl/specs/latest/2.0-compute/
[2]: https://9ballsyndrome.github.io/WebGL_Compute_shader/webgl-c...