Remove the word “category” in the h1 of the categories.

In the editor, click the Archive title block, and there’s a setting for whether it should show or not.

Thanks for your answer @audunmb, you mean the category editor, I can’t find that option.

No, the site editor.

If you use a Full Site Editor-theme like TwentyTwentyTwo or -Three: Go to Edit templates, then find the Archive or Category template and find the Archive title block in the template.

If you use Twentig with a classic theme you probably should ask the theme developers instead.

For the Twenty Twenty-One theme, add the following CSS code in the Customizer > Additional CSS panel to remove the “Category:” text :

.archive-title-prefix {
	display: none;
}

Hope that helps,
Yann