Dear community,

honestly, I do know almost nothing about ConTeXt. My sincere apologies. The answer https://tug.org/pipermail/lualatex-dev/2018-September/001681.html on my request https://tug.org/pipermail/lualatex-dev/2018-August/001680.html implies that  this mailing list might be the right spot for my initial problem. 

Here is the initial problem: The following MWE renders correctly in XeLaTeX but not in LuaLaTeX and illustrates the problem.

\documentclass{memoir}

\usepackage{fontspec}

\newfontfamily{\burmeseFamily}{NotoSerifMyanmar-Regular.ttf}[Scale=MatchLowercase]

\begin{document}

Test {\burmeseFamily{}တော်ကြီး} foo.

\end{document}

Thank you very much for taking your time. 

Yours with many thanks, 

Campanignis.