No DNS Record for fake domain

Can I survive without a DNS record for my “fake” domain?

I would presume this is the root cause why I get a http failure response for 503 Service Unavailable while visiting the where 30186 is the port.
Then I press log in and get an unregistered redirect_uri (“”).

The .dev TLD is quite real, and domains from it resolve. Ether way, you will not receive Lets Encrypt certificates using “fake” domains. Please use the real domain.