Phabricator might be best but this mailing list works fine too. Wiki pages probably not so much as notification emails are broken ATM.
1. Make the usual WMF wiki shortcuts work, i.e. meta for metawikimedia, en for enwiki, d for wikidata, etc.
Do you have an exact list? The Wikimedia interwiki map has 400+ elements, I'd rather not pull it in blindly.
2. Install the translate extension
I have set it up on
https://wikispore-test.wmflabs.org/ . I don't know much about Translate and there are plenty of configuration options so please check how well the default settings work for the use cases you envision.
It should be enabled already.