So far, so good, but then you try to change the type of map between the available options (currently, OpenLayers, Leaflet and Mapbox GL JS) QGIS freezes and you have to close the application via Windows Task Manager. I observed the occurrence on QGIS 3.20 Odense and on QGIS 3.16 Hannover, version of qgis2web 3.16.