How to send messages to telematics hub from my custom solution via MQTT?

 Using MQTT to put the data into your flespi channel.
howtos
mqtt

MQTT usage assumes that you have a good technical background. This may be written on first demand. However, we have everything explained here: https://flespi.com/protocols/mqtt.

See also
How to complement missing message parameters with telemetry values?
Using plugins to add cached telemetry values in place of missing device message parameters.
howtos
messages
plugins
telemetry
How to move devices from account to subaccount?
An API method to change the owner of the registered flespi device.
accounts
devices
howtos
subaccounts