A major milestone for Linebender: we've just published fearless_simd v0.2: https://github.com/linebender/fearless_simd/releases/tag/v0.2.0
Thanks Laurenz Stampfl and Andrew Jakubowicz for the heavy lifting for this release, and Daniel McNab as well.
We're not claiming this is stable yet, and it's missing some things like swizzle, but we've been using it very effectively in vello_cpu and vello_hybrid for 2D rendering tasks. It supports ARM, x86_64, and WASM SIMD, all portably and safely, and with runtime dispatch. Try it out.