The Help > Whats This? function (.uno:ExtendedHelp) can only show extended tooltips if help is installed, so either the entry should be disabled or if help isnt installed and the function is clicked, an error dialog should appear stating that help needs to be installed before this can be used.
I vote for a "notification" dialog along with either means to reload the help or static text how to do so.
"Error dialog" sounds too escalating to me, and we should clearly distinguish notifications from errors not only in the wording here but also in the visualization.
I too think a "notification" should appear.
This seems obsolete to me. With switch to browser for display of local help, neither extended help nor "Whats This?" work at all. Therefore the condition "if help is installed" has become irrelevant.