I’m really struggling to type Vietnamese into Anki, and no matter what I tried, it does not work. My only workaround is to type the text somewhere else, i.e chrome, firefox, and note then paste it into Anki. I’m using ibus Bamboo 0.8.1, the latest Anki and Zorin OS 15.3
Have you tried downgrading from Qt6 to Qt5?
It doesn’t work
It may be due to this: https://docs.ankiweb.net/editing.html#unicode-normalization
Try adding the flag it mentions to your Anki, it may be incorrectly trying to convert the Vietnamese characters.
It isn’t proper to Vietnamese, there are some diacritics that can’t be input directly in Anki, for instance in decomposed á (a then ´), which is very common in some languages (Spanish, Irish…). I asked about it a fairly long time ago, Damien replied that it depended on some library (it must be that Qtx) and that he had no mastery over it. So the only thing to do is to use the same workaround as Goku does, and wait until that library become Unicode conformant.
For what it’s worth, on Windows 10, I use Unikey software (configured for VNI method) to type Vietnamese into Anki and it works fine. Unikey is also available for Linux.