What are some alternatives?
When comparing Undeveloped and Domainz.io, you can also consider the following products
Nuage - Nuage provides domain naming services.
Short Domain Search - Find short, available single-word domain names
DomainWatch - Domain Monitoring Made Easy
Brandpa - Domain names for startups
Selldom - Make money from your unused domains 💸
Domainr - Domainr