How to use selnolig package together with default lualalatex font?

Question

Edit: Included different variants to show that everything seems to work fine.

I'd like to use selnolig with the default font used by lualatex. The reason is that I write a paper using the Simplified LNCS Template (which is based on Springer LNCS conference template). The template uses the default latex font. When the workshop organizers publish on CEUR-WS.org (as we do in the ZEUS workshop), we do not need to double-check with Springer.

Introduction into selnolig

selnolig works fine when using fontspec. Here an example with "TeX Gyre Termes: "workflow" has a ligature and "dwarflike" not.

\documentclass{article}
\usepackage[ngerman,english]{babel}
\usepackage{fontspec}
\usepackage[english]{selnolig}
% hint by http://tex.stackexchange.com/a/321066/9075 -> enable "= as dashes
\addto\extrasenglish{\languageshorthands{ngerman}\useshorthands{"}}
\setmainfont{TeX Gyre Termes}
\begin{document}
\noindent
workflow -- ligature is correct here\\
dwarflike -- no ligature (automatically)\\
dwarf{\breaklig}like -- no ligature (manually, using selnolig)\\
dwarf"|like -- no ligature (manually, using babel)
\end{document}

MWE without fontspec

\documentclass{article}
\usepackage[ngerman,english]{babel}
\usepackage[english]{selnolig}
\addto\extrasenglish{\languageshorthands{ngerman}\useshorthands{"}}
\begin{document}
\noindent
workflow -- ligature is correct here\\
dwarflike -- no ligature (automatically)\\
dwarf{\breaklig}like -- no ligature (manually, using selnolig)\\
dwarf"|like -- no ligature (manually, using babel)
\end{document}

Result

! Package selnolig Error: ==========================================
(selnolig)                Error Alert Error Alert
(selnolig)                ------------------------------------------
(selnolig)                The selnolig package *requires* the
(selnolig)                'fontspec' package, but it hasn't been
(selnolig)                loaded. Exiting now.
(selnolig)                ===========================================.

MWE without setmainfont

\documentclass{article}
\usepackage[ngerman,english]{babel}
\usepackage{fontspec}
\usepackage[english]{selnolig}
\addto\extrasenglish{\languageshorthands{ngerman}\useshorthands{"}}
\begin{document}
\noindent
workflow -- ligature is correct here\\
dwarflike -- no ligature (automatically)\\
dwarf{\breaklig}like -- no ligature (manually, using selnolig)\\
dwarf"|like -- no ligature (manually, using babel)
\end{document}

Result

MWE with fontspec and switching back to lmodern manually

From the documentation:

If the selnolig package is run under LuaLaTeX but the fontspec package isn’t loaded by the time the \begin{document} statement is encountered, selnolig will terminate with an error message.

So, I tried to set an arbitrary font and then switch back to the default font:

\documentclass{article}
\usepackage[ngerman,english]{babel}
\usepackage{fontspec}
\usepackage[english]{selnolig}
% hint by http://tex.stackexchange.com/a/321066/9075 -> enable "= as dashes
\addto\extrasenglish{\languageshorthands{ngerman}\useshorthands{"}}
% hint by https://tex.stackexchange.com/a/24998/9075 -> switch back to latin modern
\setmainfont{TeX Gyre Cursor}
\renewcommand\rmdefault{lmr}
\renewcommand\sfdefault{lmss}
\renewcommand\ttdefault{lmtt}
\begin{document}
\noindent
workflow -- ligature is correct here\\
dwarflike -- no ligature (automatically)\\
dwarf{\breaklig}like -- no ligature (manually, using selnolig)\\
dwarf"|like -- no ligature (manually, using babel)
\end{document}

The result is as follows.

Question

Are there any issues in just loading fontspec and not to use setmainfont?

Answer 1

The question is not very clear but I think you are looking for

\documentclass{article}
\usepackage{fontspec}
\usepackage[english]{selnolig}
\usepackage[ngerman,english]{babel}
\addto\extrasenglish{\languageshorthands{ngerman}\useshorthands{"}}
\begin{document}
workflow\\
dwarflike\\
dwarf"|like
\end{document}