I wish I could help, but I don't have a Fubo TV account and I'm pretty sure I'm permanently banned because i used more than one free trial. 
I would look into using URLs that contain https://link.fubo.tv. Perhaps seeing if there are links in the web UI somewhere that go to a specific channel and using whatever path they have specified there.
$ adb shell dumpsys package com.fubo.firetv.screen
Activity Resolver Table:
Schemes:
fubotv:
c823270 com.fubo.firetv.screen/tv.fubo.mobile.presentation.onboarding.dispatch.controller.DispatchActivity filter 27a266e
Action: "android.intent.action.VIEW"
Category: "android.intent.category.DEFAULT"
Category: "android.intent.category.BROWSABLE"
Scheme: "fubotv"
Authority: "app_open": -1
Authority: "al": -1
http:
c823270 com.fubo.firetv.screen/tv.fubo.mobile.presentation.onboarding.dispatch.controller.DispatchActivity filter ccc110f
Action: "android.intent.action.VIEW"
Category: "android.intent.category.DEFAULT"
Category: "android.intent.category.BROWSABLE"
Scheme: "https"
Scheme: "http"
Authority: "link.fubo.tv": -1
Authority: "link.fubo.tv": -1
Path: "PatternMatcher{PREFIX: /}"
Path: "PatternMatcher{PREFIX: /}"
AutoVerify=true
https:
c823270 com.fubo.firetv.screen/tv.fubo.mobile.presentation.onboarding.dispatch.controller.DispatchActivity filter ccc110f
Action: "android.intent.action.VIEW"
Category: "android.intent.category.DEFAULT"
Category: "android.intent.category.BROWSABLE"
Scheme: "https"
Scheme: "http"
Authority: "link.fubo.tv": -1
Authority: "link.fubo.tv": -1
Path: "PatternMatcher{PREFIX: /}"
Path: "PatternMatcher{PREFIX: /}"
AutoVerify=true
Edit: Also, can Fubo be added to the Live tab in Google TV? If so you can run adb logcat on that device and see what commands are run when you load the channel from the Live tab.


, i.e. you need a lot more than that: