I have wondered many times.
Of course I can always use a browser but it’s overkill.
The same goes for yad or zenity, they pull in webkit which is a full-fledged browser engine, and at least yad does not have an offline mode.
I just want to look at some local HTML (incl. images) & CSS styling.
If you’re wanting to view the rendered page, then you’re looking for a browser. Even if whatever you use doesn’t support something like javascript, it’d probably still be considered a browser?
If you don’t care about all the styling, there are tools to extract the main content and convert it to markdown.