If you find yourself having to build a multi-lingual site in Modern SharePoint, behind-the-scenes you will leverage the Multilingual User Interface (MUI) option. Although this feature is automatically configured for you, there are some things to be aware of.
Note: Variations is a former technique used in Classic SharePoint to accommodate multiple languages where you had multiple versions of the same content translated by machine translation services or manually. Variations is not an option in Modern SharePoint as of this time.
In this post, I’ll show an example of using MUI on a Modern Communication site.
Whether you create a modern Communication site or Team site, you need to select a default language at the time of creation. This can’t be changed later, however the site can be viewed in other languages by leveraging the MUI feature.
MUI Option
After the site is created, you can enable different languages for your site. This is done from Site Settings…Language settings. 
This works in tandem with the end-user’s profile language setting. If an end-user had German selected as their profile language, the site would appear in German. There are, however, exceptions to this and I’ll list what is and isn’t translated to the alternate language and how to address the gaps.
Automatically Translated
Any Microsoft-provided text in standard UI elements will be automatically translated for you. Examples:
- Site name
- Home link
- Edit link
- Following link
- Share site
- New link
- Search this site
- Out-of-the-box column names (Title, Created by, Modified by)
Not Translated, but Fixable
Custom text entered by an end-user will not be translated, however you can edit (some of) them to the alternate language. Examples:
- custom navigation items (except for Hub links!)
- custom column names
- document library names
To fix the above items, from your Delve profile, change your default language to the alternate language you want to update. (You may have to wait awhile (up to 1 hour) for the change to take effect) Once it has, edit the navigation items, custom column names, and library names to the alternate language. This will only change it for the alternate language and not the default one. Cool!
Not Translated, Not Fixable
The following content will not be translated into the alternate language and will display in whatever language has been entered:
- File names
- Item names
- Page content
- Text modern web part text
- Hero modern web part text
- Quick links modern web part text
- Hub navigation links
- Highlighted Content Web Part content
Currently, the only workaround I’m aware of is to include multiple languages to accommodate all alternate languages. For example, the title in the Hero web part below displays both English and French for all users regardless of their language setting:
My thoughts
For organizations needing to accommodate multiple languages, this can be a cumbersome process. Any place where free-form text is entered will always be displayed in the language it was entered with (makes sense). If it’s critical for content that isn’t automatically translated to be displayed in multiple languages, the only option is to display them as I’ve shown above. However, this is really only a suitable option for 2 languages.
Thanks for reading.
-JCK