replacing the current domain of the lightsail instance with another domain

Hi.

If your GoDaddy domain also manages DNS, add a record to point to your Lightsail instance's public IP address.

If you don't have DNS with your GoDaddy domain, point your current DNS server's NS records to your GoDaddy domain.

Hi,

Thank you for using Lightsail. Can you please provide some more details on what you are attempting to achieve?

The procedure may be similar to managing DNS using Lightsail only: https://lightsail.aws.amazon.com/ls/docs/en_us/articles/understanding-dns-in-amazon-lightsail