What does that mean? How do you access HN through CloudFlare and what do you mean by AWS not supporting TLS1.3? You can certainly run any https server on EC2, including one that supports TLS1.3.
$ dig +noall +answer A news.ycombinator.com
news.ycombinator.com. 0 IN A 50.112.136.166
$ nslookup 50.112.136.166
166.136.112.50.in-addr.arpa name = ec2-50-112-136-166.us-west-2.compute.amazonaws.com.