Beautiful, blissful black. Nothing but that.

I had already disabled all the elements of the page that you can, and I wanted a dark theme, so in addition to filling a void in dark theme support (with a void), it got rid of the remaining useless bits. Perfect. (well, not completely perfect as pointed out by others, there's a flash of white; maybe I'll try the workaround... but I doubt there's anything the extension can do about it)

(btw it took me way too long to figure out there's a built in dark theme in Firefox, it's just not in the Options, but in Customize)