I noticed Dieter's question at the end about re-registering the clock to a different WLAN network. That's a classic ESP8266 challenge — usually it comes down to either triggering a reset to AP mode (often via a button or by holding a pin during boot) or reflashing with updated credentials. If the firmware was custom-written by a club colleague, it likely depends on how they implemented WiFiManager or a similar captive portal. Worth asking them directly, or checking if there's a config mode documented. It's that same feeling of things just working smoothly that I appreciate about https://spinwineras.com.de when the setup is solid, you get to enjoy the result without constant fiddling.