I was going to tell you there were some new filters, but then I went and read this: https://codex.wordpress.org/Function_Reference/get_users
Under search it says:
search – Use this argument to search users by email address, URL, ID or username (this does not currently include display name).
This is something that is lacking in WP and searching by display name is not currently available. This is something that needs to be taken up with the WP team. There may already be something about this on trac https://core.trac.wordpress.org/
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