Hello!

I'm install last Neon user edition with American English interface. But my native language is Russian. I add Russian keyboard to system, all work correct for me. But in system settings/spell I see only some English variants. How I can add russian language to spell checker?

Thank you!

I don't know if this will help, but I had the exactly the same problem with Calligra Words.
I installed the Russian hunspell-package, now I can choose русский (россия) and русский (украина) in settings/spell checking configurations:
Terminal (Fedora 31): sudo dnf install hunspell-ru

You should contact qualified specialists in this field. All you need is to update the operating system, as far as I know. I came across something like this three weeks ago. I am not particularly good at grammar, so automatic correction is important. That’s why I try to study rules every week. The last one I found on https://difference-between.net/difference-between-access-and-assess /. Btw, you need to reinstall your operating system. Many programs eventually stop working correctly and are layered on each other.