Yes, that’s true, but
when Strapi tells me that it listens to http://0.0.0.0.0:1337 I guess that it listens on all interfaces of its host or docker contaoiner for that matter. Therefore Strapi is reachable from the outside.
When Strapi tells me that it listens to http://127.0.0.1:1337 I guess that it listens on the loopback interface of its host or docker container. Therefore Strapi is NOT reachable from the outside.
This is the case with the installation I mentioned on my post. 127.0.0.1 and not reachable.
The problem is that I can not find any hint as to why Strapi uses 127.0.0.1. No envmironment variables, nothing.
The following lines in config.server.js
host: env('HOST', '0.0.0.0'),
port: env.int('PORT', 1337),
tell me that host is either the value of $HOST or 0.0.0.0.
Now $HOST is not set, so host: should be 0.0.0.0 but apparently it is 127.0.0.1 – hence no external access.