In recent versions (can't say from exactly when), there seems to be an off-by-one error in dcc.DatePickerRange. I set max_date_allowed = datetime.today().date(), but in the calendar, yesterday is the maximum date allowed. I see it in my apps, and it is also present in the first example on the DatePickerRange documentation page.

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Solution that would be nice its additional field "crosshairMarkerColor" to addLineSeries settings

const lineSeries = chart.addLineSeries({
    crosshairMarkerVisible: true,
    crosshairMarkerRadius: 6,
    crosshairMarkerColor: '#111',
});