The border between Liberland and Croatia is now officially open. There's an official border crossing and you can get to Liberland without trying to avoid the croatian border police.
Another "non-land" use-case is that you can start a Liberland company and issue invoices. Even though Liberland is not recognized by many countries, that is usually not a problem for business - Taiwan is not recognized by many countries, but Taiwanese companies do business easily.