okay … but where ?
The unit is set to Kelvin and according to the openhab UoM Documentation the conversion between units should be done by the OH framework
I was wrong! Setting the channel “unit” results only in a changed unit-sign and not in a conversion. I must have missunderstood something. Sorry for that! @rossko57 Thanks for stepping in!
Assuming your sitemap Text widget does not have a label= to override that given in the Item…
Note that sitemap based viewer will need a refresh to pick up edits in this area.
It sounds for all the world like your Item label is ignored.
Confident there is no muddle over Items?
Confident there are not both UI and file based versions?
You can see in your events.log what Item is getting changed by MQTT, and what to.
Try editing your Items file, retype that [presentation] in case of stray invisible character, make sure file loads as evidenced in your openhab.log
Change label text spelling, is that change seen?
I have to say the way I expect this to work is for binding to pass 290 K to Item, but Item to use [presentation] as default units when supplied, and convert to 17 C at the point of updating.
If true, still points at missing [presentation]