Serious probs installing frigate, MQTT, Mosquitto

Having a heap of trouble with (I think) permissions, when trying to setup the above.
Everything installed, and (sort of) running, but mosquitto will not stop complaining about not being able to access the /mosquitto/config file.
Checked permissions and looks like the data is owned by 1883, but there is no such user/group, and other directories are owned by me…
Can somebody point me at the definitive source for setting this up??
Thanks.

Which Home Assistant installation method do you use?

Sorry, Docker…
Currently checking out videos on mosquitto install…

Rather than do it all at once, did the “add Mosquitto, then add Frigate, then get the integrations working”, and it worked…
Still had a couple of ‘gotchas’, but working now… mostly…
Got to figure out HOW it works, now!
Thanks.