I’m aiming to use the picture glance card in Lovelace, but I can’t work out where to put the image file on a Dietpi. I’ve checked that the directories are all owned by the ‘dietpi’ user (which seems to be the norm for a Dietpi). I’ve placed the image in: /mnt/dietpi_userdata/homeassistant/config/…

In other words the path you want is /mnt/dietpi_userdata/homeassistant/www not /mnt/dietpi_userdata/homeassistant/config/www