Hi, thanks for your support. And I know that you guys tried to fix it. However, it hasn’t worked well yet.
I tested it today on my Chromebook, with the same font family (Open Sans). Open Sans does support Vietnamese.
This is how the Vietnamese letters with tones look like on Windows 10 (and of course this is the standard shape of Vietnamese):
And this is how they look on Chrome OS:
As you can see, letters ê, ô, â, ă and i look messy with tones.
It may not be an error of Chrome OS, because I tried typing Vietnamese with Google Docs on Chrome OS. And here is how they look:
They look as normal as standard Vietnamese does. Hope that you will find out the bugs and fix them.