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

Just weaken the magic, the connection to Arcat, and everything related to it in this version of the dwarves (I don't know why, maybe they have fewer midichlorians, haha) and they'll happily use cannons and rifles.
Another option is, by the way, technomancy. Gunpowder isn't the only way to provide the propulsive force for a projectile; fire mages could easily use something like micro-explosions that they generate themselves. It's even quite possible that this path would be much more obvious and competitive with combat magic. Because throwing a fireball a long distance should be relatively difficult for a mage; not everyone can do it, but detonating something in their hands so that the resulting pulse sends something forward – even a weaker mage could handle that.
In the world I was working on a long time ago for a forum, I actually used both of these ideas to make the dwarves technologically advanced.

by the way, yes! I completely forgot about magic! There are cannons that shoot fireballs with a power source in the form of a fire crystal.

and here's what I came up with regarding mages and non-mages:

Difference #1 - these dwarves dug themselves underground at the very beginning of the War of the Ancients, and only emerged after the first eclipse, pale and red-eyed.

Difference #2 - the dwarves tried to restore the system of governance as in the Shanti Empire: priests rule, and the rest live happily under their rule (they failed).
This created a magical elite that abuses its power and immense strength.

Then, among the peasantry, alchemists appeared, producing medicines, and then gunpowder and the first gunpowder-based weapons appeared.
Moreover, all of this happens underground, meaning there's no hunting; firearms became the weapon of bandits, and they were made by blacksmiths of less-than-stellar skill