I thought it sounded familiar!
I think it’s worth trying to get a solution working with nodered (not node.js) nodered is so much simpler. If you can get that to work you could then look at triggering the nodered flow from webcore.
Other solutions that may work -
There is an app (VM) homebridge that brings non apple homekit devices into homekit. There is a plugin to control marantz/denon amps, there maybe one for yours. You’d then have to get homekit & webcore integrated. Its a lot of work & rather convoluted, but may depend on how much you need the functionality.