Voicemail performance is still a fragmented mess on Android because each manufacturer designs their own dialer app, and each carrier builds its own visual voicemail app.
According to a ticket posted to the Android Issue Tracker, support is coming for T-Mobile, Project Fi, and Orange in France. Because there are several months to go before Android M comes out of preview, we sincerely hope it will become operable for other networks as well.
Why this matters: Visual voicemail is one of the few remaining holes in the stock version of Android. If you want you can send your voicemail to Hangouts, but it’s a jagged implementation and Google Voice’s transcription is terrible. The carriers and various manufacturers will of course tinker with what Google designs, but at least this pushes visual voicemail into the core of Android.