You need to pay for it.

The domain name registration is free for the first year. After this period, Odoo will continue to manage the domain in partnership with Gandi.net, the domain name registrar, and you will be charged Gandi.net’s renewal rate. Odoo sends a renewal quotation every year to the email address mentioned in the Domain Owner form several weeks before the expiration date of the domain. The domain is renewed automatically when the quotation is confirmed.

From https://www.odoo.com/documentation/17.0/applications/websites/website/configuration/domain_names.html#register-a-free-domain-name-with-odoo