terraform-aws-modules/terraform-aws-alb v9.0.0 on GitHub

9.0.0 (2023-10-27)

target_groups previously were defined by an array of target group definitions that were created using the count meta-argument. This has been replaced with a map of target group definitions that are created using the for_each meta-argument in order to provide better stability when adding/removing target group definitions.
target_groups no longer support multiple targets per target group. There are alternate methods to achieve similar functionality such as weighted target groups or using an autoscaling group as a target when targetting EC2 instances.
The previous methods for creating listeners have been removed in favor of one argument, listeners, which take a map of listener definitions that are created using the for_each meta-argument in order to provide better stability when adding/removing listener definitions. Previously the target_group_index was used to associate/reference a target group; that is now replaced with target_group_key which is the key of the target group definition in the target_groups map.
security_group_rules has been replaced by security_group_ingress_rules and security_group_egress_rules to align with the new underlying resources.
Minimum supported version of Terraform AWS provider updated to v5.13 to support the latest features provided via the resources utilized.
Minimum supported version of Terraform updated to v1.0
The Name tag has been removed from resources

Security group attachment restrictions have been removed now that both ALB and NLB support security groups
Support for creating Route53 records for ALB/NLB DNS names via the route53_records variable

enable_cross_zone_load_balancing now defaults to true
drop_invalid_header_fields now defaults to true
enable_deletion_protection now defaults to true
associate_web_acl has been added to identify when a WAFv2 Web ACL should be associated with the ALB; previously this was accomplished by checking for the presence of a value passed to web_acl_arn which is known to cause issues when the value does not exist and is computed.

See UPGRADE-9.0.md for further details