RTF is a global modification that replaces all towns in the game.

Is Linna's death mandatory?! - Where did that come from? If new campaigns try to stay within the lore, their plot should not exclude all possible endings of Dark Messiah!!!
- Can the player ensure that Linna survives? Answer: Yes, they can!!!
- Can the player ensure that Linna dies? Answer: Yes, they can!!!
Therefore, the human race can fall, or it may not, but it is not specified when exactly (tomorrow or in a hundred years), meaning that humans must exist, but it is quite possible that not in the form of a unicorn empire, but as part of something else; moreover, the fall of the human race does not imply extinction as a species, but implies a fall as an independent empire.

I found this information a long time ago in the comments on the website for the 7th Heroes game:

Sareth did free the demons, but they did not conquer the world; instead, they became, let's say, "aggressive neighbors" to the other races. With the arrival of the demons in Ashan, the cycles of eclipses ended, and cycles of the Void began. In general, the demons became Ashan's enemy number 2, and the Order of the Void of Sandro took the dominant position. I have no idea what the future holds for this. The information was taken from Erwan's presentation on Ashan.