I'm new to Humax - just four days - but having installed Kodi Matrix 19.3, I have successfully installed Netflix in there. It needed a bit of fiddling to set up and a bit of tweaking, but it now runs perfectly.
Instructions here: https://github.com/CastagnaIT/plugin.video.netflix
Troubleshoot here: https://github.com/CastagnaIT/plugin.video.netflix/wiki/FAQ-%28Errors%29#Request-failed-validation-during-key-exchange