LOOHP
Is it the same for every other item? Or does it only happen to specific items?
I've just tested on a 1.21.4 server with 1.21.4 client and 1.20.4 server with a 1.20.4 client on the latest dev build #303. I was unable to reproduce this problem...
The language of that item name in chat should be dependent on the client language and not the language option in the config. Perhaps you have another chat plugin that...
Which build of ProtocolLib are you running?
The corrsponding update in ICPE still haven't been released yet. It is merged and tested already and will be published soon.
Your paper build is probably not up to date.
It seems like ChatManager is the one doing the final command dispatch that is triggering the error. You might want to contact them about it.
I think the correct way to fix this is to fix the underlying cause which is this being incorrect on Folia. https://github.com/LOOHP/InteractiveChat/blob/870ef661877e5f1fa5ec4f01bb3a2461a36b7f34/common/src/main/java/com/loohp/interactivechat/api/events/ICPlayerEvent.java#L45
In my experience, it should work with join messages but not leave messages. Is that also the case for you at the moment?