ViewHelpers removed from TYPO3 

Debug.render ViewHelper <f:debug.render> was removed 

TYPO3 v15.0 removed the ViewHelper. Use the Render ViewHelper <f:render> instead. If typo3/cms-adminpanel is installed, it replaces <f:render> with its own implementation. Every <f:render> call then shows the Fluid debug output when the option Show fluid debug output is active in the Preview settings of the admin panel.

The debug argument is only available while the admin panel is installed. Without the admin panel, Fluid throws an exception for this undeclared argument.

Form.datePicker ViewHelper <formvh:form.datePicker> was removed 

The DatePicker form element type and its associated <formvh:form.datePicker> and <formvh:form.timePicker> have been deprecated in favor of the Date form element.

Form.timePicker ViewHelper <formvh:form.timePicker> was removed 

The DatePicker form element type and its associated <formvh:form.datePicker> and <formvh:form.timePicker> have been deprecated in favor of the Date form element.

InfoboxViewHelper state constants moved to ContextualFeedbackSeverity enum 

The public constants in InfoboxViewHelper for defining the state/severity of an infobox have been removed. Use the enum \TYPO3\CMS\Core\Type\ContextualFeedbackSeverity instead.