There is an "Underline" type in pandoc's definition (https://hackage.haskell.org/package/pandoc-types-1.22/docs/Text-Pandoc-Definition.html#t:Inline https://hac

There is an "Underline" type in pandoc's definition (https://hackage.haskell.org/package/pandoc-types-1.22/docs/Text-Pandoc-Definition.html#t:Inline https://hackage.haskell.org/package/pandoc-types-1.22/docs/T...). In Pandoc's format, this works like: This word is [underlined]{.ul}.