access fonts installed through LaTeX with XeLaTeX

Question

I don't have e.g. Helvetica, yet would like to use its clone that can be used with pdflatex, but instead use it with xelatex. I have tried

\usepackage{fontspec}
\usepackage{helvet}
\newfontfamily{\phv}{Helvetica}

Which tells me fontspec can't find Helvetica.

\usepackage{fontspec}
\newfontfamily{\arial}{Arial}
\usepackage{sectsty}
\allsectionsfont{\arial}

Which works, since I'm on a windows machine and arial is installed.

%\usepackage{fontspec}
\usepackage{helvet}
\newfontfamily{\phv}{Helvetica}

Which works with pdflatex. Switching back

\documentclass{article}

\usepackage{fontspec}
\setmainfont{Libertinus Serif}
\usepackage{helvet}
\setsansfont{Helvetica} % <-- doesn't work, since I don't have the font installed on my system
%\newfontfamily{\phv}{Helvetica}
\renewcommand{\familydefault}{\sfdefault}

\section{first section}

some text which should be in helvetica

\end{document}

MWE that I wish to be working:

\documentclass{article}
\usepackage{fontspec}
\usepackage{helvet}
\newfontfamily{\phv}{Helvetica}
\usepackage{sectsty}
\allsectionsfont{\phv}

\begin{document}

\section{first section}

some text which should not be in helvetica

\end{document}

I'm sorry, but I won't take the time to get into LuaTeX atm. I'm at a loss as to what I should try, and how, and in which order.

Answer 1

Use the clone TeX Gyre Heros:

\documentclass{article}

\usepackage{fontspec}
\setmainfont{Libertinus Serif}

\setsansfont{TeX Gyre Heros}

\renewcommand{\familydefault}{\sfdefault}
\begin{document}
\section{first section}

some text which should be in helvetica

\end{document}