See PHI1674. If you do not have Excel export support installed and try to export data, you get a <select /> with "Excel (Not Available)" as an option, and must click a button labeled Download Data to actually get instructions. Although there is technically a path to success here, it is far from obvious.
Ideally, we would not require an external for Excel support, which would moot this. It's not currently clear to me how feasible first-party Excel export support is, but it may be realistic because we need only a very narrow range of features (cell formatting in a single output sheet).
Failing that, the option should be disabled and this dialog should offer a link to some sort of "Manage Export Formats" page which shows installed exporters and provides instructions for enabling any which are missing dependencies.