Hi,

Underline support for tty frames was added to Emacs back in the Emacs
28.0.90 release. It hasn't worked for me since. Today I tried
investigating why. I tracked it down ncurses and discovered the tgetstr
function to retrieve the escape sequence for underline support doesn't
fetch the value configured in the terminfo database for my Terminal
(st). I can reproduce this function failing to fetch the entry in a
minimal sample program (code attached).