How to create an SSL certificate for an AWS application load balancer without a domain
Solution 1:
Option 3 is the only valid one. Have the user to create a Route53 domain and ACM cert beforehand and provide the domain name and certificate ARN as parameters for the CloudFormation template.
Provide a README.md your GitHub repo with instructions on how to do that. ACM certs are free, no reason why not to use them.
Hope that helps :)