When I compile the following document I see in the output localized
variants for the various glyphs. But copy & paste works only for the
last line. The first two gives notdef chars.

In the pdf e.g. the first glyph has the numbers 2D0E, 2D0F, 2D0D in
the three lines but only for the last there is a unicode mapping:
<2D0D> <5203>.

What can one do to get a mapping also for the other glyphs?

The font can be downloaded here
https://github.com/adobe-fonts/source-han-sans/blob/release/OTF/SourceHanSansJ.zip
A related bug report is
https://github.com/adobe-fonts/source-han-sans/issues/200


\pdfvariable compresslevel 0
\pdfvariable objcompresslevel 0
\setupheader[state=stop]

\starttext

\font\zhs=
{file:SourceHanSans-Regular.otf:mode=node;script=hani;language=ZHS;+locl}
\zhs 刃令毒骨縣誤

\font\zht=
{file:SourceHanSans-Regular.otf:mode=node;script=hani;language=ZHT;+locl}
\zht 刃令毒骨縣誤

\font\test=
{file:SourceHanSans-Regular.otf:mode=node;script=hani;language=DFLT;}
\test 刃令毒骨縣誤

\stoptext