We would like to contribute further german translations, since there are still some parts missing, e.g. in the postorious interface. Would https://translations.launchpad.net/mailman/3.0/+pots/mailman/de/+translate be the right place to do so, so that everybody could use our translations?
If there are other areas in which you could use our help, please let us know.
I wanted to set it up, but the requirement is to use a free hosted solution. (So transifex and crowdin are a no-go, they would be great to get translations, especially crowdin looks very active in that regard) I tried out zanata.org but it's extremely slow... The other option at the time was pootle (http://pootle.translatehouse.org), which doesn't offer hosting but some folks at gnu had a customized instance set up, but they discontinued the service.
I searched for a translation service for a private project and found weblate.org . They offer hosting (hosted.weblate.org) for open source projects and it looks like a couple of people are using it. You need to contact them if you want to set it up for an open-source project though and I didn't want to invest in it without knowing what the end-result would be...
Since I'm also mainly interested in German translations for my own installation, I opted to just use plain .po files and filed merge requests against the repositories. Postorius has translations (not perfect, but a start for the moderators that use my instance) included by now but my merge request for core is still outstanding https://gitlab.com/mailman/mailman/merge_requests/400/ Since I don't use Hyperkitty, I didn't translate that.