Cannot install themes

The frontend supports themes. This category is for sharing themes.

I have this in my configuration.yaml

frontend:
themes: !include themes.yaml

and a themes.yaml in the same dir as config.yaml

I cannot choose a different theme, what is going wrong ?

Your indentation is wrong. See Home Assistant Frontend - Home Assistant

like this ?

frontend:
  themes: !include themes.yaml

still not working

I think the way to do it is

  themes: !include_dir_merge_named themes