In network load balancer to API Gateway with 5443 port

maybe the following can help you

Create a Network Load Balancer Specify the appropriate VPC and subnets where your API Gateway resides.

Create Target Groups:

1. HTTP Target Group: with Protocol: HTTP, Port: 5443 (Attach your API Gateway instances or relevant endpoints.)
2. HTTPS Target Group: with Protocol: HTTPS, Port: 5443, (Attach your API Gateway instances or relevant endpoints.)

Configure Listeners:

1. HTTP Listener: with Port: 80 (HTTP) and Forward traffic to the HTTP target group you created
2. HTTPS Listener: with Port: 443 (HTTPS) and choose a valid certificate for your domain and Forward traffic to the HTTPS target group.

DNS Configuration: Create a DNS record pointing your domain name to the Network Load Balancer's DNS name.