There’s a public API for google Assistant. Pretty sure you need to be signed up as a google developer ($5 once off fee) to set it up though, but I did that setting up Home Assistant and it was easy.
Then you can connect a docker to it. I had a quick look already on the docker hub but I’m not sure it’d work on the iHost and can’t see how to connect it to the eWeLink Cube anyway. Without the eWeLink Cube you could turn the iHost into a Google Home Speaker and could send instructions from the iHost that pretend to be a voice. Controlling the devices on the iHost using Google Assistant would also be nice but I think you’d need to adapt the docker image.
There’s the annoyance of that once off $5 fee though. Maybe because you already have Google Assistant connected to eWeLink you could bypass that step though.