https://archive.mozilla.org/pub/thunderbird/nightly/latest-comm-central/

but only en-US is available. Nightly trunk builds are not localized

Thanks for your answer. My interest is for other languages, not the en-US. I know the nightly builds are not localized, but the xpi files for others languages were available until October the 16th when a change in the repositories directories happens (now by year and month). If till this date the languages xpi files were available, I thought these files could also be moved to a different place.

The problem is https://bugzilla.mozilla.org/show_bug.cgi?id=1222878