If I understand you have a remote sensor that works on low power (with a battery I think) and you must get all the temperatures in a central server.
If you need few frequencies data (more than a minute) I think the better solution is to write a simple Gateway that
- send a message to the device and wake It;
- the client sends back the temperature;
- the gateway sends a message to a central server;
You can do that with a WOR of LoRa device
Ebyte LoRa E32 device for Arduino, esp32 or esp8266: WOR (wake on radio) microcontroller and new Arduino shield – Part 6
And use a free (limited) service like AWS for the Gateway
AWS IoT core and MQTT services: connect esp32 devices – 4
If you need high frequencies data simply send the data from the client to a gateway that send all the data to the central server.
If you need a dashboard with all widgets pre-created you can use Blink, Arduino IoT, or Adafruit IO, but exists several IoT dashboards like that all free.
If you want use thethingnetwork with your device you can use the Arduino Library
https://www.thethingsnetwork.org/docs/devices/uno/quick-start/
Bye Renzo
