WebGL not working in Safari 18.2 in MacOS 15.2 on iMac15,1 and OCLP 2.2.0

The update went very smoothly but WebGL in Safari isn't working - e.g. on site https://get.webgl.org it says Safari supports WebGL but I don't see the spinning cube. I need WebGL for tinkercad.com which works fine in Chrome on this system.

After googling I did set this preference:

defaults write com.apple.Safari WebKitPreferences.webGLEnabled 1

but still no spinning cube.

I haven't a more current Mac where WebGL works fine with the same versions of Safari & MacOS.