I used the ticket system because AFAIK that's the official method for contributing with translations to APT.
Also the Weblate project you mentioned is being used as an intermediary place for us, Brazilian Portuguese, to translate some projects. Place notice the slug part "ptbr". It is not the official place for the Brazilian Portuguese team and is not the official place by the APT team to receive translations.
It is worth mentioning that I'd love to have a APT translation project in that Weblate instance as the official method. As administrator of the Weblate instance, I'd be more than happy to help setting it up.
Best regards,
Rafael