Case C-817/18 P: Judgment of the Court (Second Chamber) of 9 September 2020 — Vereniging tot Behoud van Natuurmonumenten in Nederland and Others v European Commission and Others (Appeal — State aid — Aid scheme relating to the subsidised acquisition or free granting of nature land — Preliminary examination procedure — Decision declaring the aid compatible with the internal market — Action for annulment — Admissibility — Regulation (EC) No 659/1999 — Article 1(h) — Concept of ‘serious difficulties’ — Service of general economic interest — Secondary activities — Related actions)