> it's one of the first games that is using ECS and that I also have a deep interest into

Both, at the same time :)

ECS probably been around since at least early 2000s if not even in the 90s.

Edit: Wikipedia puts Thief as the "pioneer" of ECS:

> In 1998, Thief: The Dark Project pioneered an ECS. (https://dev.to/ovid/the-unknown-design-pattern-1l64) The engine was later used for its sequel, as well and System Shock 2.

I think it's one of the first games heavily using Unity DOTS, which probably also explains its launch troubles.

Unity's new ECS system I assume, not ECS as a general architecture