When viewing different instances, whether to copy a community link to make another instance aware of it & subscribe to it or otherwise, it would be nice to have a switch along the top bar to switch between admin-set light/dark mode themes.

That way you aren't either forced into being blinded by light mode or having to let your eyes adjust to dark mode. Admins could choose the variant of light or dark theme to have the switch toggle between, so in the case of more customized instances they could retain their distinct style.

For reference, see almost any site with a light/dark toggle, but for a closer example, see Piefed's approach.