How to connect to an internet-facing Application Load Balancer using its internal IP addresses

How can I connect to an internet-facing Application Load Balancer using its internal IP addresses?

Situation:

• Multi-Account Setup using a centralized Network Account
• Within the Network Account, there is an internet-facing Application Load Balancer used for our IdP / PingFederate
• Applications hosted in AWS should connect to IdP / Application Load Balancer using its internal IP addresses

Issue:

• I am not able find a way on how to resolve the internal IP addresses of the internet-facing Application Load Balancer using a comfortable approach

What I tested:

1. Utilize Route53 "Default .2 Resolver" -> Issue: It resolved only to the Public IPs of the ALB
2. Created Private Hosted Zone with my IdP's URL, and create an A Record Alias to my ALB -> Issue: Again, it resolved only to the Public IPs of the ALB
3. Created Private Hosted Zone with my IdP's URL, and create an A Record the internal IPs of the ALB's ENIs -> Issue: Internal IP addresses of an ALB may change, hence this is a setup where I need additional coding (e.g. running a Lambda every few minutes to update my PHZ entries)

Looking for any input that may help.