Reported on bugzilla <
https://bugzilla.wikimedia.org/show_bug.cgi?id=40383%3E
Just beat you to it :) It is now tracked in https://bugzilla.wikimedia.org/show_bug.cgi?id=40380
yeah :)
It seems UW is not using some new unified plural-rules JS file, so all languages with plural rules are broken. The workaround we chose was to redirect the UW to the English version. We hate it, but it's better than to have no upload at all.
We did the same for French. Better than nothing