Horrible 3D/Three.js performance in latest Safari on macOS

I just tested the latest Safari Technology preview (15.0, R128) on macOS 11.5 and Shadowmap runs perfectly fine, maybe even faster! If that’s where this all is going, I’m happy and hope for fall …

On the other hand, some three.js demos are still super slow (e.g., three.js examples).

Any other updates from other people affected by this?