Destination URL needs (at least a semi-)opaque background
While hovering over a link, that link's destination is shown in the lower left corner.
The text has no background, so it can be hard to see depending on the site.
With the default theme, Adwaita, the text blends in to dark backgrounds; with Adwaita-dark, it blends in to light backgrounds.
How about a 50% transparent background for this text?
Not quite sure what this element is called (in the old days, browsers had a "status bar" there which also served this function); so here are some screenshots to illustrate (circled in red):
Adwaita, dark text on page with light background.
Adwaita-dark, light text on page with dark background.