Here's my MWE, it appears replacing MedeivalSharpwith any TTF file will do the trick.
\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{fontspec}
\usepackage[osf,proportional]{Baskervaldx}
\usepackage{polyglossia}
\newfontfamily\msharp[
Path = {/home/kristian/.fonts/},
Extension = .ttf
]
{MedievalSharp}
\begin{document}
{\msharp{This is Medieval Sharp.}}
But this is not Baskerville.
\end{document}
fontenc. Also, as @UlrikeFischer mentioned, don't loadBaskervaldx. Use\setmainfontfromfontspec. – Oleg Lobachev Jan 14 '20 at 18:46Oleg Lobachev -- Duly noted, thanks.
– Kristian Nordestgaard Jan 14 '20 at 19:10