Provision multilingual sites with PnP templates

Sharepoint PnP Powershell library (which is also available on Nuget) has own provisioning engine. It is quite powerful engine which allows to provision MUI sites (although it has own problems with stability). In order to do that you need to use several basic elements:

1. Have all literals which should be localized in resx file

2. Specify supported languages inside <pnp:SupportedUILanguages>…</pnp:SupportedUILanguages> section of PnP template. After provisioning these languages will be set in Site settings > Language settings > Alternate languages. You need to have resx file for each supported language in standard resources.xx-XX.resx format

3. Resx files with translations should be specified inside <pnp:Localizations>…</pnp:Localizations> section of PnP template. Note that PnP will provision all these languages to your site regardless of what alternate languages are set in Site settings > Language settings on the moment when this template is applied to target site

4. For localized strings use {resource:ResourceKey} format inside template

Here is example of how PnP template for MUI site provisioning may look like:

<?xml version="1.0"?>
<pnp:Provisioning xmlns:pnp="http://schemas.dev.office.com/PnP/2018/01/ProvisioningSchema">
  <pnp:Localizations>
 <pnp:Localization LCID="1033" Name="English" ResourceFile="resources.en-US.resx"/>
    <pnp:Localization LCID="1031" Name="German" ResourceFile="resources.de-DE.resx"/>
  </pnp:Localizations>
  <pnp:Templates ID="Test-Container">
    <pnp:ProvisioningTemplate ID="Test" Version="1">

      <pnp:SupportedUILanguages>
        <pnp:SupportedUILanguage LCID="1033" />
        <pnp:SupportedUILanguage LCID="1031" />
      </pnp:SupportedUILanguages>

   <pnp:SiteFields xmlns:pnp="http://schemas.dev.office.com/PnP/2018/01/ProvisioningSchema">
  <Field ID="..." Name="MyField" DisplayName="{resource:MyFieldTitle}" Type="Text" Group="Custom" SourceID="..." StaticName="MyField"></Field>
   </pnp:SiteFields>
   
    </pnp:ProvisioningTemplate>
  </pnp:Templates>
</pnp:Provisioning>

It will provision file with English and German UI languages.