I don't want to use private CA and create private certificates. Is it possible to create public certificate using ACM for internal (NOT internet facing) ALB ? If yes then how can it be created ? As per below ACM FAQ looks like it should be possible but i am not able to figure out how can it be created ?
Q: Can I use public certificates for internal Elastic Load Balancing load balancers with no public internet access?
Yes, but you can also consider using ACM Private CA to issue private certificates that ACM can renew without validation. See Managed Renewal and Deployment for details about how ACM handles renewals for public certificates that are not reachable from the Internet and private certificates.