\input luaotfload.sty

\font\testa={file:lmroman10-regular:script=latn;+tlig;+trep}           at 10pt
\font\testb={file:lmroman10-regular:mode=node;script=latn;+tlig;+trep} at 10pt
\testa ``fi `fl' ffi--ffl---ff'' \par
\testb ``fi `fl' ffi--ffl---ff'' \par
\bye