WebEngine rendering not working

[StefanKaiser-TomTom]

Hi,
thanks a lot for the plugin, and the recent change to enable WebEngine for the preview. Sadly it doesn't work for me. After clicking Exporter (WebEngine), the preview window opens, but

• the exporter just states initializing preview
• the preview-panes is empty
• the developer tools window does not render anything
• the logs don't show anything

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| QGIS version | 3.40.0-Bratislava | 
| QGIS code revision | 1d561ad8ad9 | 
| Qt version | 5.15.2 | 
| Python version | 3.9.5 | 

Following https://github.com/minorua/Qgis2threejs/wiki/How-to-use-Qt-WebEngine-view-with-Qgis2threejs, I installed for the QGIS-python (/Applications/QGIS.app/Contents/MacOS/bin/pip):
PyQtWebEngine==5.15.7
PyQtWebEngine-Qt5==5.15.15

maxOS is 15.0.1 (24A348)