Minecraft1.20.1 modloader 0.1635 in the last version of the mod.
I install the last version of the mod and I get multiple warns in my console who said: [Server thread/WARN]: Failed to deserialize component: unregistered key travelersbackpack:travelersbackpack_entity
It's a new feature who do this or it's a bug to fix?

This is warning, you use travelersbackpack on the save that previously used older version. travelersbackpack:travelersbackpack_entity component has been deleted in latest release and backpacks that spawn on entities are handled differently. It's just a warning, nothing to worry about. It won't happen in newly created worlds