The Filter Everything PRO and Free plugins are compatible with WPML and allow you to create translations of Filter Sets to use according to the current language on a site. This is not necessary and you can use the same Filter Set for all languages on your site. But if you want to translate Filter Labels, then it is better to create translations. To do this, you need to make the Filter Set translatable Post type in the WPML settings -> Settings -> Post Type Translation as it is shown on the screenshot below
If you use different domains for your languages, please do not forget to enable CORS.
If you translate your WooCommerce products and you want to use translated Filter Sets for them and you want to filter by product variations, please do not forget also to explicitly set Variations as translatable post type in WPML Settings.
Note: if filters in the translated Filter Set do not display terms, try to reset the cache by adding the parameter ?reset_filters_cache=true to the URL of your site page. For example https://example.com/?reset_filters_cache=true – open the page and the set of terms will be updated.
With Polylang PRO
In the case of Polylang PRO, the ability to translate Filter Sets and SEO Rules should be available by default. You just need to open any Filter Set or SEO Rule and create a translation for it. If this option is not available, you have to activate Filter Set and SEO Rules as translatable post types in Polylang PRO Languages -> Settings -> Custom post types and Taxonomies.