I kind of like Mastodon's multicolumn "advanced web interface", except that the columns are fixed-width and far too narrow.

Apparently the way people mess with this if they want to is to adopt a user stylesheet, but this is probably too much to ask of most users (the world intended by CSS's designers in which user stylesheets are universal, sites are all designed to work well with them, and there are popular tools to manipulate them never really came).