So it looks like your apex domain is working fine.
Your subdomain is going through CloudFlare, but it looks like it’s serving infinite redirects. Are you sure you have the correct CloudFlare setting? If CloudFlare is proxying over HTTP to Caddy, then Caddy will respond with an HTTP->HTTPS redirect. Just a guess for what’s happening.
Your Caddy logs only includes the startup sequence, and nothing after startup. It should show some reverse_proxy logs if Caddy gets that far. Did you copy your logs before making requests, or is nothing getting logged when you make requests? If nothing is logged, then you definitely have a problem with CloudFlare not sending requests to your server correctly.