I would continue to use Random User-Agent, however, I had to uninstall due to its breaking of Youtube. With RUA enabled on Firefox, YT's homepage yields only grayed-out slots where the videos should be shown -- obviously I can't interact with anything, let alone watch a video.
This error persists across the most recent versions of both Firefox and Waterfox. I had to disable all of my extensions and turn them on, one-by-one, and in the end, only RUA has this effect on Youtube.

Will gladly re-install in the future if this problem is resolved.