The Slingbox M1 is compatible with any set top box that has the correct outputs (Component/Composite); however, we do not have the exact Humax model within our base sources. You can view our base sources using this tool within our articles:
Now, the coding for that remote is likely the same as one of the other Humax remotes. As this specific model is not a base remote coding that we have listed, you do also have the option of a Custom Remote. I've linked the Custom Bin File upload process article, as well as the remote forum page that contains the Humax remotes, below for ease of access:
I hope this helps!
Sling Media Technical Support