A website with only one language activated is really quite different from a website with multiple languages activated. After adding a language the next step is not known.
After activating multiple languages, tell the user what steps to take now in possibly activating extra modules and make settings to content types (and possibly more, but I don't know now)
TBD
Possibly: show extra (modal?) screen for administrators that activate a second language
TBD
Closed: outdated
9.5
(Drupal 8 Multilingual Initiative) is the tag used by the multilingual initiative to mark core issues (and some contributed module issues). For versions other than Drupal 8, use the i18n (Internationalization) tag on issues which involve or affect multilingual / multinational support. That is preferred over Translation.
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