There’s nothing within the SmartThings platform as provided by Samsung that supports MQTT that I know of.
There have been multiple community projects that create MQTT integrations, but they all depend on having a separate server device to act as the MQTT broker.
Here’s the most popular one, I believe, but there are others as well.
Integration Solutions using MQTT
As far as what you’re seeing, not sure what’s going on there. Can you post a screenshot?
Tagging @orangebucket just in case he knows of anything.