Since the new update, I have not been able to type Vietnamese characters in * .md files.
Currently I have to disable this plugin to be able to use.
I hope the author will fix this problem in the next versions.
Vietnamese keyboard inf at unikey.org
There is a really old issue (#41) about this.
I am not sure whether it is the same issue. But I suggest deleting the onBackspaceKey keybinding registered by this extension.

It is working, thanks!
Most helpful comment
There is a really old issue (#41) about this.
I am not sure whether it is the same issue. But I suggest deleting the
onBackspaceKeykeybinding registered by this extension.