CSS text-decoration family (not just for underlining links)
Text-decoration | HTML & CSS Wiki | Fandom
Stefan Judis on Twitter: "I can't wait for all these new text-decoration properties to be widely supported. It's still early stages, but broader support of properties to e.g. define the underline thickness
How to underline text in CSS - javatpoint
CSS Text Decoration Module Level 4
css - Remove blue underline from link - Stack Overflow