Case C-691/20: Order of the Court (Ninth Chamber) of 22 October 2021 (request for a preliminary ruling from the Tribunal Judicial da Comarca do Porto Este — Penafiel — Juízo Trabalho — Portugal) — B v O, P, OP, G, N (Reference for a preliminary ruling — EU law — Principles — Article 18 TFEU — Equal treatment — Discrimination on grounds of nationality — Prohibition — Article 49 TFEU — Freedom of establishment — Joint and several liability of companies which form part of a group for debts resulting from an employment contract entered into by one of those companies — Exclusion by the legislation of the Member State concerned of companies that have their seat in another Member State)