Hi,
Yes, you can use other hardware, but it’d need to send data in the same format so that it’s ingested properly. The sensors would need to be registered on the platform if they are not already (https://api.smartcitizen.me/v0/sensors), and the IDs in there should be used to send data over, so that the “marriage” between sensor data and its storage happens correctly.
The token can be obtained from the onboarding process (start.smartcitizen.me). That token will be used in the MQTT topic, and as soon as valid messages are being sent using that token, you will be able to see the device online.
Check this other topic for more info: Sensors readings from a DIY kit! How to integrate into SmartCitizen?