Sadly 1) Apple only, 2) soft deprecated.
I imagine it will still be around for a long time because Apple and a lot of large third party apps use it for simple 3D experiences. (E.g. the badges in the Apple Fitness app).
Apple wants devs to move to RealityKit, which does support non-AR 3D, but it is still pretty far from feature parity with SceneKit. Also RealityKit still has too many APIs that are either visionOS only or are available on every platform but visionOS.
Microrant: I absolutely loathe when I am told "move to new thing. Old thing is deprecated/unsupported" and the new thing is incredibly far from feature parity and usually never reaches parity, let alone exceeds it. This is not just an Apple problem.
In general, it suffered from the problem of even Apple not knowing what it was made for, and what it even is. For a 3D API, it has less features than OpenGL 2. For a game engine, it… also has way less features than the competition, which shouldn’t surprise anyone - game engines are hard, and the market leaders have been developed for _decades_. But that’s what it looks like the most - a game engine. (It even has physics.)
Customizing the rendering pipeline in SceneKit is absolutely horrible. The user is given a choice between two equally bad options: either adding SCNTechniques which are configurable through .plists and provide no feedback on what goes wrong with their configuration (as like 3D rendering isn’t hard enough already), or using “shader modifiers” - placing chunks of Metal code into one of 4 places of the SceneKit’s default shader which the end users _don’t even have the source code of_ without hacking into the debug build! Or pulling it from Github from people who already did that [_].
If you just need something that can display 3d data, SceneKit is still fine, but once there’s a requirement to make that look good, it’s better to throw everything away and hook up Unity instead.
[_] https://gist.github.com/warrenm/794e459e429daa8c75b5f17c0006...
I find SDL3 more fun and interesting, but it’s a ton of work to to get going.