Your workspace is on an active Hobby plan with no custom domains currently attached, so you should have the option to add custom domains. The screenshot you shared shows the workspace-level Domains page, which is for purchasing domains from Railway. To add your own custom domain, navigate to one of your services (e.g., kelnar-client or kelnar-server), open its Settings tab, and look for the "+ Custom Domain" button in the Public Networking section. If that button is also missing from the service settings, please share a screenshot of that page so we can investigate further.

Oh, i've missed that one, thanks bot for pointing me in the right direction. Marking this as resolved!