<texcode>
\startsetups [chapter:after]
\ifcase\rawcountervalue[footnote]\relax
\or
\setuphead[chapter][aftersection=\setups{chapter:after}]
\starttext
\startchapter[title={Chapter One}]
This one\footnote{is placed}. And\footnote{this one is too}.
\stopchapter
\chapter[title={Chapter Two}]
But this one\footnote{is not flushed}.
\startchapter[title={Chapter Three}]
Unless \type{\stopchapter} was invoked.
\stopchapter
\startchapter[title={Chapter Three}]
On a chapter with\footnote{footnote}.
\stopchapter
\stoptext
</texcode>