Question about TP-Link Tl-Mr6400

Hi. We use the device in the holiday flat in Ticino for the internet and also for heating control (Viessmann Vitoconnect Opto1). It works perfectly.

Hy
If the smart appliances are controlled via the app, it works perfectly. However, if you want to address individual IP devices via the router, this only works if a fixed IP (clarification with the provider) is assigned on the router for access.
Since you access the provider via the SIM, you are assigned an IP by the provider, but this IP is not publicly accessible behind the provider's router. If you query the router IP on the computer via myip.com, this does not correspond to the IP in the router itself, but is that of the provider. This means that remote access to the router is also not possible, unless you get a fixed IP!