Can you do customisation with Sass when theme is set to none?

[rossbowen]

Description

I am setting theme: none in a HTML extension I am creating, but I wondered if it was possible for me to still provide styling using Sass?

[mcanouil]

Did you try in a simple document? Sometimes, it's faster to just try.
Note that SCSS files should be provided to theme (https://prerelease.quarto.org/docs/output-formats/html-themes.html).

Be aware that theme: none means everything that Quarto does for the layout (e.g., grid layout, navbar, sidebar, etc.) won't be there. It's not only about colours and fonts.
You should really try it first and see what this means exactly, as I highly doubt, it's what you want especially if you are working on website/book extensions.