Where do they come from? How long do they take to update? Any way to force update?
Do they come from the in-package manifest or do they come from the "Channel Poster" on the "Channel Store Info" screen? Does the same answer apply to both private channels and public channels?
I updated a private channel with updated in-package home screen icons, and also updated the "Channel Poster" on the "Channel Store Info" screen. My Roku got the private channel update however I still see the previous home screen icon.
Any details about how to update and control the update of the home screen icons would be very much appreciated.
From my understanding, the channel icon used is the one you upload to the dev portal, and it only updates when your channel is published/approved. That means your private channel or private vanity code for public channels will update as soon as you publish. Public channel icons will update once your channel has been approved after submitting it. The icons in the manifest are used for sideloading, but maybe they are also used for published (private or public) channels when you are offline, unless Roku caches all the installed channel icons.
note: this is only evidence from my own experience