Right now (17/12/2024) the documentation about how to implement UL is really outdated. There isn't a full source of true. Let put all together here.
Is the simpler step, but is important to understand a few things.
- You need to control domain's dns.
- the root domain is always "your-domain.com" (without www or protocol)
- The domain "www.your-domain.com" is considered like a subdomain. the subdomain is www and the domain the rest.
- Also subdomains like, "app.your-domain.com" is considered a sub domain (of course).