There is a bug in the code for searchUserByDisplayName related to capitalization. It returns no matches if the search term is capitalizes even if the display names are capitalized.
Sample display names in my instance: William Brady, william williams, Frank Williams.
// searchTerm Will, only will williams
UserRepository.searchUserByDisplayName({ displayName: 'Will', limit },({ data: users }) => ...)}
// search term will, all 3 are returned
UserRepository.searchUserByDisplayName({ displayName: 'will', limit },({ data: users }) => ...)}