'R loop for Kruskal-wallis test with confounders?

I have a large dataframe 2000 subjects (into 3 groups) x 80 observations . I have multiple questions.

They are not normally distributed. Do I check normality for each observation group-wise or whole data?
I need to perform kruskal-wallis/anova for all 80 observations between these groups. I found a code:
R: Kruskal-Wallis test in loop over specified columns in data frame

but this doesn't account for confounders. Is there a way to add it in the formula?

r loops normalization

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