Two language versions for each article

I have a WordPress website that needs to be available in two different languages. We have the articles written in both languages already.

I’ve seen a lot of solutions providing automatic translations but this won’t work in this situation because we have to use translations produced by government approved translators.

What would be a good solution to allow each article to have 2 versions and allow switching between them with a button or dropdown?

I think and use the way about an WP Multisite install, see my answer, background, information and benefit on a older question.