Next step is to find out how to activate port 9898 on the device or find another approach to do the same.
I can see that 9898 is not active listening…
Update:
As on other pages written, the system on this version of Mi Smarthome hub (gateway) also referred as v4 works differently. And there seems to be no way to get a developer key from somewhere. Further more I cannot identify which service on the device would be related to to port 9898.