-> install build dependencies:
$ tce-load -i compiletc gettext-dev libidn2-dev ncursesw-dev readline-dev pkg-config openssl-1.1.1-dev

-> make two changes to the configure file:
1. change this: 
  for ac_lib in '' tinfo curses ncurses; do 
to this: 
  for ac_lib in '' tinfo curses ncursesw; do

2. change this: 
  for ac_header in curses.h term.h ncurses/curses.h ncurses/term.h termcap.h
to this: 
  for ac_header in curses.h term.h ncursesw/curses.h ncursesw/term.h ncursesw/termcap.h

-> make two changes to src/lftp_tinfo.cc
1. change this:
#else
# error No header file for tigetstr or tgetstr found. Install ncurses-dev or termcap-dev.
#endif

to this:
#else
#  include <ncursesw/term.h>
#endif

2. change this:
   if(setupterm(NULL, 1, &errret) == ERR)

to this:
   if(setupterm(NULL, 1, &errret) == -1)

-> per TCL wiki, for maximum compatibility:
$ export CFLAGS="-mtune=generic -Os -pipe"
$ export CXXFLAGS="-mtune=generic -Os -pipe"
$ export LDFLAGS="-Wl,-O1"

-> and finally...
$ ./configure --prefix=/usr/local --without-gnutls --with-openssl
$ make