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

I think it can still be integrated into the original lore. Goblins already have firearms (pistols); we can connect it to that. For example:

To improve their hunting, the northern peoples decided to use more advanced weapons. With the diligence characteristic of dwarves, they improved the mages' pistols, equipping the guns with longer barrels and a larger charge of gunpowder. Armed with such weapons, dwarf hunters can pierce any armor, but not at very long range.

To make an accurate shot from that angle 😉

Not bad, by the way, about gunpowder, do you know what it's made of? Sulfur, saltpeter, and charcoal (originally, ground roots were used instead of charcoal).
Sulfur and charcoal are simple, but saltpeter was extracted from MANURE; now it's clear why firearms are only available to goblins – the others are too squeamish! In a world full of mages, only creatures devoid of magic will develop firearms.

Added 27 minutes later
Now about Ashan.
I have a few ideas that don't fit into the concept of Ashan.
For example, a faction of human fanatics who have rejected magic because they were oppressed by mages (this would replace the orcs).
And, of course, abandoning Ashan will allow us to create normal green orcs (and bash the humans, WAAAGH!).

There's no need to think up the lore; it's enough to say that there is a world of spirits, there were 2 gods, but they killed each other, and now the great spirits are in charge. All races come from one proto-race, and Ashan's tears can be replaced with shards of a god.
The rest can be figured out as we add factions.

This lore allows us to create as many races and as many gods as we want, and not just 6 + we don't need to add factions just for the sake of it, like an alliance of elves and dwarves, just to indicate their presence