I thought I had seen a way to map an MQTT On/Off to Open/Closed but I can’t find it. Is it possible or do I need to use a rule?
Yes, you can do it.
Go to your contact item by using the main ui
under metadata → state description → options
There you paste for example:
Has this actually to be done for every item or can this also be done globally for e.
g. a contact with OPEN/CLOSE. This would make it easier to get it language specific.
Yes, you would have to configure this for every item. Alternatively, you could configure a rule that captured these events (using a group to capture the item) and convert the state as needed.