Question: What would be the best way to support themes?

[michaelstonis]

What would be the best way to approach automatically supporting a dark mode or other theme for the generated output? Would that require a custom renderer or extension to modify the output HTML and add additional CSS classes?

[xoofx]

What would be the best way to approach automatically supporting a dark mode or other theme for the generated output? Would that require a custom renderer or extension to modify the output HTML and add additional CSS classes?

Nope. Any rendering related topics are delegated to CSS, especially dark mode that is usually implemented differently by the different CSS framework providers (CSS variables, SCSS...etc.) requiring often additional JavaScript.