There's a new game in town for portable, multiversioned Rust SIMD: fearless_simd. It's still early days (we're gearing up for an 0.2 release soon), but we are using it very successfully to accelerate rendering algorithms in vello_cpu and vello_hybrid. I believe it represents the best compromise on stable Rust today. We're not saying it's ready for production use yet, but I encourage people exploring this space to try it and give us feedback on how well it works.
There's also a big discussion to be had about how the Rust language might more natively support SIMD. There are some hacks in fearless_simd to work around limitations in the language (especially relying on inlining as load-bearing), and it would be excellent to make that more robust. But the best path forward is not obvious.