One thing I noticed about Volla OS 12.1 on my Volla 22 is the lack of settings to have the phone vibrate along with emitting a notification sound when receiving an SMS. The easiest way to have it vibrate is by setting the phone on "Do Not Disturb" or silent mode. But then you won't have any sound when you receive SMS. You cannot have both simultaneously.
Even when you open the notification settings for the Messages application, there's no setting to have the phone vibrate on received SMS:
However, after spending a lot of time, I finally found a way. The key here is to enable notifications history in Settings > Notifications > Notification history > Use notification history.
Once this is enabled, wait until you receive an SMS (or send an SMS to your own number). The notification will appear in your notifications history, which you can access by sliding the top menu down and pressing the History button:
If you press on it, you will be redirected to the same page where you enabled it. Below, you can see the list of past received notifications. Now, if you perform a long press on an SMS notification, you will see the notification settings for the Messages application, except that it looks a little bit different because you opened it from within the notifications history. It looks similar but with more options. Now, if you look below, there's an option to enable vibration:
From now on, your phone will always vibrate for incoming SMS, except when you are inside the Messages application.
Edit: Alternatively, you can press on the button with a bell icon which says "~1 notification per day" which is visible on the first screenshot. That will also send you to the different notification settings.