\definefontfeature [node-smcp-tlig] [mode=node,script=latn,smcp=yes,tlig=yes]
\definefontfeature [base-smcp-tlig] [mode=base,script=latn,smcp=yes,tlig=yes]

\definefont [testfontnodesmcptlig] [file:linlibertine_r.otf*node-smcp-tlig]
\definefont [testfontbasesmcptlig] [file:linlibertine_r.otf*base-smcp-tlig]

\startTEXpage[offset=1ex]
    \start \testfontnodesmcptlig gnu - gnat -- foo --- foo \stop
    \par
    \start \testfontbasesmcptlig gnu - gnat -- foo --- foo \stop
\stopTEXpage
