Hi,
There’s an extensive thread at The Employment Gold Card Super-Thread
Essentially, there is no ‘other’ category (unless one of the ministries announces an entirely new field for everyone just to get your friend in), and applicants are required to select which (single) ministry will process the application.
The process is very document-driven. Which set of evidentiary documents best represent your friend as a talent? Match that up with one of the categories and submit.