I just found another novel at Kakuyomu that has a "diverse" protagonist.
Here it is :
https://kakuyomu.jp/works/1177354054881348443
Name : 砂塵の王 ( Sajin no Ou )
Author : 秋山 和
Chapters ( Ongoing ) : 200 Chapters
Summary. The protagonist is a brown-skinned knight from a desert kingdom. I take it that it's modelled/inspired from an Arab or Middle Eastern-like country/region. I just read only 2 chapters so far, but from what I came to know, it has these elements :
1. High Fantasy not Isekai
2. Has lizardmen and dogmen in it
3. Apart from the MC and his race/ethnicity of brown-skinned people, there's also a black-skinned human race here modelled/inspired from African people.
4. Just read only 2 chapters so am not sure if White people and characters would be included too for added diversity later on in future chapters. As well as for Japanese/Far Eastern-like characters.....