This is an interesting one which I thought I would bring to your attention though I realise you can’t support any software that anyone throws at you.
For some time now on many boards I have always installed Mosquitto with Websockets… and it has always worked without issue.
Two of us have now tried this with the same results - installing Mosquitto with Websockets on DietPi - it works just as normal… however it does not start automatically on power up.
Using Webmin you can see that the service is there. You can RESTART the service - and it starts - no problem, - but…it will not start up on it’s own on powerup.
We have a way around it - to take the “restart” part of the startup script - put it into /etc/rc.local - and it works perfectly but this is not ideal really.
Anyone have any thoughts as to why this might be?? ONLY in DietPi - works fine on a standard Raspberry Pi, or with a “standard” Armbian distribution.