Behind your own nginx or Apache

If ports 80/443 are already used, let Caddy serve plain HTTP on another port and proxy to it. In .env:

SITE_ADDRESS=:80
HTTP_PORT=8088
HTTPS_PORT=8443
APP_URL=https://pos.yourcompany.com

nginx (keep the Host header, allow WebSockets):

location / {
    proxy_pass http://127.0.0.1:8088;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}