I used the default MiSans, I have tried google San, Milan Pro, Roboto they all have the same issue, I have another phone, redmi k20 pro, I am using custom firmware miui ori base on miui13 china, but it doesn't have this issue.
On miui13 and miui14, there is small issue with my redmi k40s. Font is error when display Vietnamese in facebook or some webpage. In miui china, I can fix by turning off miui optimization, but in eu rom, that option is hidden. I have attach the image, please help me check it.