Hangouts, Google Voice, and SMS is no longer supported Notification Although I have been a long time user of Google Voice and Hangouts, I only recently got my first Android tablet(WiFi only, no cellular).  

The way the first two interact with the tablet is puzzling and frustrating:


As far as I can tell Hangouts is the tool that Google wants us to use for Google Voice SMS messages.
It seems that recently Google removed SMS support from Hangouts except for Google Voice SMS that is still supported, and provided a way to choose what app to use as the main SMS app.
With Hangouts installed everything seems to work but I get constantly spammed by a Hangouts notification saying that SMS is no longer supported.  I have found no way to silence this notification unless I disable all Hangouts notifications, which would make me miss other Hangouts IMs.
In the attempt to silence the SMS is no longer supported spam notifications I tried to install other SMS apps, but since my tablet is WiFi only, I am unable to install them.
I only found one SMS app that would install without the cellular hardware (I think called Messenger) and it spammed me with so many advertising Notifications that I had to uninstall it, The cure was worse than the illness.


I hope the community can help me find a solution, either by pointing me to a way to silence the Hangouts "SMS is no longer supported" notification, or by pointing me to a messenger app that will install on a WiFi-only tablet and stay nice and silent (which is ideal as I probably will never use it, I would only install it to silence the Hangouts notification).

Thanks.
I had the same problem and I also wanted to avoid installing an extra app just to get rid of a notification. 

The only thing I could think of is Facebook messenger which I already use. After I downloaded it the notification disappeared and messenger was now the default app for SMS.

In case the notification doesn't disappear automatically go to:

Settings -> Apps -> (Gear Icon top right) -> Default Apps

and you should see 'SMS App' just tap on it and choose messenger(or any other app you want to try). My tablet has Android 6.0.1 so instructions may differ on other versions.

PS. Firstly I tried to revoke any SMS permisions to hangouts so I can clear it from the default app for SMS but it didn't work.