This plugin adds Polylang support for WordPress Customizer.

• Language switcher in Customizer.
• Localized theme_mods and options for both default and custom made Customizer values.
• Enable/disable forcing “The language is set from content” setting in Language > Settings > URL modifications

1. Polylang must be installed and activated.
2. Languages must be set in Admin > Languages.
3. If you have a static front page:
   1. Create a front page per each language.
   2. Select the front page in Admin > Settings > Reading per language.
4. Expect customizer to use setting type = theme_mod (default) as in:

$wp_customize->add_setting( 'setting_id', [ 'type' => 'theme_mod', ] );

This plugin can be installed directly into your plugins folder "as-is"
or:

• go to Plugins > Add new and type in Search Add Polylang support for Customizer and click Install and then Activate buttons.
• if you go to Admin panel > Plugins > Add new > Upload Plugin and select the archive containing this plugin.

It's safe to activate the plugin at this point. Because the plugin just injects some functionality - there will be no plugin menus or settings to play with. License

This plugin is licensed under the GPL v2 or later; however, if you opt to use third-party code that is not compatible with v2, then you may need to switch to using code that is GPL v3 compatible.

For reference, here's a discussion that covers the Apache 2.0 License used by Bootstrap.

Original solution made by @soderlind is available here. Share some love! This is WordPress plugin version of his solution.