I like the greybird and greybird-dark themes, I think greybird is the default with xubuntu. (edit - there are a ton of themes out there: https://www.xfce-look.

I like the greybird and greybird-dark themes, I think greybird is the default with xubuntu. (edit - there are a ton of themes out there: https://www.xfce-look.org https://www.xfce-look.org Though personally I would avoid using their app)