Hi @onis_csadi I believe the calendar widget is available in grist-omnibus, but it currently requires two extra environment variables to actually show up in the UI. They are:
PERMITTED_CUSTOM_WIDGETS=calendarGRIST_WIDGET_LIST_URL=https://github.com/gristlabs/grist-widget/releases/download/latest/manifest.json
With those two set, I see the calendar widget offered in the latest docker image for grist-omnibus.
There are some improvements coming to Grist that will make these settings unnecessary, but that’s the current situation.