\documentclass{article}
\usepackage{garamondx}
\usepackage[acronym,smallcaps]{glossaries}
% % This is a workaround (with line above commented out)
% \usepackage[acronym]{glossaries}
% \renewcommand*{\newacronymhook}{%
%    \edef\tmp{\noexpand\textsc{\the\glsshorttok}}%
%    \expandafter\glsshorttok\expandafter{\tmp}%
% }
% \renewcommand*{\acrpluralsuffix}{\textup{\glspluralsuffix}}
% % End of workaround

\newacronym{SNR}{snr}{signal-to-noise ratio}

\begin{document}

This is the call to the \glspl{SNR}.

\end{document}
