(Unknown) is a catch-all credit attached to games where the company responsible for the development or publication of the game is not listed in the game information.
If the game has not yet been published, it should be credited to (Looking for a publisher) instead.
If the game is known to be published by the designer themselves, without using a publisher brand, the game should be credited to (Self-Published) (if it has a physical form) or (Web published) (if it has only been published in a digital form).
To make a correction to an item that is (Unknown), do not add publisher- or game-specific information to this entry, as it is attached to hundreds of database items. Instead, use the Submit Corrections button in the relevant game entry(-ies). Before you can list a publisher with a game which is not yet in the database, you must first add that publisher at Misc --> Add Publisher.