How does your router support Route53?
Does your router have a static IP address and you just created an entry in Route53 mapping a subdomain.example.com to the static IP of your router?
DuckDNS is a Dynamic DNS and can work with common dynamic IPs...
How do you update the entry in Route53 when the IP address of your router changes?
My router supports no-ip and other dyndns providers. I expect if that particular router supports Route 53 than it'll do the same: just update the entry in Route53.
OPNSense saves an AWS keypair. When it detects my IP changes, it updates a Route53 record using the AWS API. It’s one of the options alongside a bunch of other DDNS providers.