[silvestrov]

The problem with monolingual is the thought that there is One True Language.

It isn't so. I write half my emails in one email, the other half in another. Often emails will have sections in one language (e.g. quote from another email) and other sections in a different language.

Spelling tools must be able to detect language automatically to be of any value and be able to handle multiple languages within a single sentence!

[Semaphor]

I use LanguageTool [0] as an extension, it never has issues detecting if I’m currently writing in English or German. I sadly have yet to find a solution that works as well on my Android.

[0]: https://languagetool.org/

[mcv]

I've managed to set my phone to accept and suggest both in English and Dutch. Works reasonably well.