Created attachment 105393 [details]
The current behavior.
The European Portuguese spell checker which comes included in the installation doesn't use the orthographic agreement of 1990 (the most recent). It's necessary to change this because this is what Portugal officially adopted between 2010 and 2012. The best option would be to include both dictionaries but use the orthographic agreement as default.
Currently it's necessary to download and install the orthographic agreement dictionary manually from https://pt.libreoffice.org/dicionarios-extensoes-e-modelos/ (Dicionário em versão Acordo Ortográfico).
The UI itself uses the agreement (try writing "atualizações" too, just like in the help section).
Steps to reproduce:
1. Install a fresh copy in Portuguese (Portugal) of Ubuntu 14.04 LTS (for LO 4.2) or Debian Testing (for LO 4.3) [a live session doesn't work] [amd64];
2. Open LibreOffice Writer;
3. Write "actividade" and "atividade".
Marks "atividade" as wrong, but not "actividade".
Marks "actividade" as wrong, but not "atividade".
Operating System: Ubuntu
Version: 188.8.131.52 release
In Linux LO uses the system-provided spellchecker. Complain to its maintainers.