My lamp had the original text “Spotter kjøkken”. I override the label for the tile to “Taklys”. This updates the label in the tile itself, but not in the popup where you can dim the light. The popup is stil using the original label, but I would expect that it used my new label.
It’s by design. The device name is always used in the dimmer popup. The label is just changing the label of the tile itself.
You can update the device name in your source system, but of course that will change it everywhere.
PS. Your theme looks great! It looks really similar to a design that another user put together. Did you create the CSS from scratch or was it posted on the community somewhere?
I just recently noticed this after renaming movable devices (bulbs, plugs) to a short code name due to slowly migrating hubs- from dedicated name in prior set up. I may be supportive of more control on pop-up/modal formatting.