I know similar prolems have been addressed before but changing the domain to the IP doesn´t fix it, there actually is no firewall that could block this. The address can easily be connected with a browser in the same network. The page just spits out a small string, so nothing which should be a problem to the ESP.
Yes I tried it as a complete string already, same result. Doesn´t matter if I use the ip, it is bound to the device anyway. So the only chance this is changing is when switching the router. But yes of course I´d use the domain once it works, for now this is at least avoiding any issues with the dns.
Yes this is clear!
What I did not understand is if you tried with a browser from a PC DIFFERENT from the one in which the webserver is running, you stated only "with a browser in the same network".
Please post a network diagram. Which devices are connected via Wifi? Which are connected via ethernet? Which device has the webserver? Who can access it and who cannot? Does connecting to the internet work?