A few settings you may wish to consider for your firefox’s about:config page.
browser.ml.chat.enabled = false
browser.ml.chat.shortcuts = false
browser.ml.chat.shortcuts.custom = false
browser.ml.chat.sidebar = false
browser.ml.enable = false
browser.tabs.groups.smart.enabled = false
Can’t you disable all this in the settings page?
I don’t believe so. The very first one is synced with one of the options in the settings menu, but it doesn’t look like any of the rest are.
Hmm I’m not sure what options these flip under the covers, but disabling both of them appears to be sufficient to disable the features.