I found it mentioned here Liberland – Travel guide at Wikivoyage
The Liberland Settlement Association (LSA) may help you cross the border. To do so, you must follow the following obligations:
- Contact LSA; e-mail: email@example.com, phone numbers: +385 99 841 6836, +381 64 4276428, +45 29714935
- Visit LSA base camp in Serbia; from this Serbian village, Bezdan can be reached by taking a road towards the Croatian village Batina. The camp is located right before the Croatian border. It’s about 3 km from Bezdan.
- After arrival to LSA base camp you will be required to join LSA. This means that you will have to volunteer during your stay.
LSA does not provide assistance to physically and mentally disabled persons. Persons without a valid passport and medical insurance also won’t be given assistance.
Is it still active? because its website liberlandsa.org is currently failing with a digital ocean configuration page:
And that Wiki page history puts the majority of edits to be several years ago: