I’ve seen similar questions for “low battery notification” which stealls focus, it doesn’t happen to me all notifications get displayed at the top normally (like new email), but Viber new message, and this one stealls focus, so when I type, it disrupts, and then after few sec when regaining focus, new message comes 
so very annoying.
How to prevent viber to taking focus? Sound notification is good or even to be displayed like new email from Thunderbird, but not overriding focus.
I"m on gnome with F40, no special config.
Thanks