Answering my own question here: I heard back from SmartenIt Support, who confirmed their support for Samsung SmartThings.
Their KB article: https://smartenit.freshdesk.com/support/solutions/articles/13000024568-how-to-integrate-smartenit-devices-with-smartthings
Their GitHub Repo: https://github.com/thewall7/st-devicehandlers/tree/master/devicetypes/smartenit
CC: @Scott_Barton