Some things in the list are a bit weird. Let's try to correct some things and clear stuff up. I'll start by the obvious:
Brittania Games (Chivalry & Sorcery, Land of the Rising Sun for 5e D&D) "... In this edition of the classic medieval fantasy game we have drawn on modern [i.e. Intersectional Marxist] research to present the Middle Ages as they really were; diverse and rich in cultural influences and visitors from outside Europe. If this does not reflect your vision of the Middle Ages, this is not the game for you." and "... In this edition of the classic medieval fantasy game we encourage you to break away from the bland white, male Middle Ages of yesteryear and make your game as rich and varied as the Middle Ages really were. If this does not reflect your vision of the Middle Ages, this is not the game for you” -Marxists automatically go here.
If you're running a Medieval-Authentic game in the Holy Land, or in Byzantium, or some of the Mediterranean areas, you would likely see (in the largest population areas/cities) a mix of various ethnic groups. If you were in northern France or in England, outside of the largest ports, population would be extremely native. The problem with "Brittania Games" is that they're engaging in the ridiculous bullshit of Critical Theory attempts at approaching history, where the goal is from the start to try to claim that western culture was evil (they never care about any of the atrocities of any other culture, nor do they seem to demand that any other culture be multicultural or else it is evil), they try to claim that somehow culture and race are tied together, and then try to claim that people of a given ethnic group have no claim at a "genuine culture" because there "were always people of color" in that society, but often their examples of the "always" not one in five or one in ten, it's not even one in a hundred or one in a thousand. They find the weirdest cases and the rarest exceptions, which they then try to twist into claiming was the medieval norm.
And note, even in those areas where there were cosmopolitan mixtures of ethnicities, what you didn't have was a blended globalist progressive society in the style of 2022 leftism. Which is what they always want to turn settings into, to suggest the end of history, year zero, etc.