Internationalized Omeka S

Hello everyone,
How are Omeka S multilingual projects going? We are curious to hear your developments and exchange ideas.

Our project of trilingual photo database became three symmetrical sites presenting the same items and items sets, one for each language, with the language label as site slug (fr, tr, en).
That way, we can retrieve the current locale from any page (cf [solved] How to find current page slug in theme) and rebuild the url to arrive exactly on the same page with the desired language if needed. We added a language switcher in the header (layout.phtml) in our theme so that switching is possible from any page.

We store the metadata of our items in csv files, where a field present in 3 languages is represented by 3 columns, to which we attach the language label thanks to the fork language-mapping of the CSV import module suggested above (https://github.com/omeka-s-modules/CSVImport/tree/language-mapping).
Then we display only the metadata in the language of the locale indicated by the site slug (by modifications on AbstractResourceEntityRepresentation.php).
Tags become “dcterms:subject”s, field that we set as searchable with the Metadata browse module, and independent for each language.
Unfortunately when it makes more sense to attach description to the media than to the item, the field has to be filled manually in the three languages but it still serves our purposes (cf Metadata for Media / Item set with CSV Import module?)

Stay some elements proper to Omeka S not yet translated. We generated a file with Poedit with the elements to translate we could collect on our website, but how could we start an open Transifex project to translate them?
Where could we obtain the .po files from Omeka 2, that could help for the translation of some elements?

Thank you for your future examples and insights.