In case you missed it, yesterday I released Unread 2.3 with home screen widgets for devices running iOS 14.
iOS 14 widgets can have settings. To access the settings of a widget, long press the widget and select Edit Widget from the resulting menu. All Unread widgets have a Light Theme setting and a Dark Theme setting: one for when your device is in light mode and the other for when your device is in dark mode. By default widgets use the themes set in the Unread app, but you can set a custom light mode theme and dark mode theme for any Unread widget.