Why don't I see Twitter's homescreen widget on my Android? When I go to add widgets to my home screen, I don't have any widget from Twitter available. Other widgets are appearing in the widget list, can be added, and work fine. Just nothing from Twitter. 

What could possibly be causing this? 

I am on Android 6, but it couldn't possibly be too old, as i have an even older device running Android 4.3 where the Twitter widget is available. I have the Twitter app installed, I am logged into it, I can open it and use it. The only thing that is missing is their widget for my home screen.

I have tried removing the app and installing it again, logging back in again, restarted the device a couple times, but the widget just doesn't offer, neither for the default launcher, nor in Nova Launcher.
Sorry, the Twitter widget is gone.

The Twitter widget was removed from service in the newer versions since release 6.8.0. See the report dated July 26, 2015 from Android Police. It is possible the version you are maintaining on the earlier OS was never updated (or can't be) to a widget-less version.

My Samsung S8 carries the latest Twitter App and no widget available, regardless of launcher. (I use Nova, but confirmed this too, by reverting to the default)