The only one I find that says “implemented” was for a widget on the lock screen, and this exists now (although it has been labeled “beta” for ages, but it works fine for me). The option is in Settings > Setup. The topic title was ambiguous because it spoke about widgets generally, but then the opening post specified “lock screen”, and I guess this is why it was marked “implemented” and closed.
Other than that there are none for the home screen. However, Roon (and ARC) does show in the iOS widget in the Control Center.
