btw: I found this old GitHub request to switch to mosquitto repo. So might be something coming in future.
https://github.com/MichaIng/DietPi/issues/3042
Upgrade Mosquitto.. how? Topic is solved
Re: Upgrade Mosquitto.. how?
Pls let us know if a solution is working. This could help others if they hit by similar situation. Your DietPi Team