Use the `etoolbox` package (same technique as #5213) to add the `institute` variable to `\maketitle`. Verified to work with `article`, `book`, `report`, `memoir`, `scrartcl`.

The `\institute` command is only standard in the Beamer class. Use a conditional to restrict this to Beamer output rather than output an empty command. To add this information to a LaTeX class providing an `\institute` command, use `header-includes`.