actually, the iRMG generator, starting from version 1.27, allows you to exclude the parametric chance of a mirror map appearing.
that is, it will never appear if you don't want it to.

This is only if you have the generator itself; most players won't have it, and the maps will be generated by the judges. However, players will be able to determine the races randomly by going to the same Ubisoft platform and creating a game on any map where the starting factions are not initially defined. It looks something like this: one person creates a game, for example, "Former Friends," and the corresponding colors will be assigned in advance, which the players will be informed about. Each player then creates the game, occupies their flag (red, blue), and sets the random option for the race in the parameters. After that, they load the game and see which race they get. If it suits them, they inform the judge of their race, and he then generates the map on iRMG. If it doesn't suit them, they read the rules.