\enabletrackers[otf.preparing]
\definefontfeature[mathextra][mathextra][fixitalics=true]
\setupbodyfont[stixtwo]
\setupmathematics[integral=nolimits]
\startTEXpage[offset=3bp]
With slanted integral:
\startformula
\int_0^\pi \sin x\,dx=2.
\stopformula
\setupmathematics[stylealternative={upright}]
With upright integral:
\startformula
\int_0^\pi \sin x\,dx=2.
\stopformula
\stopTEXpage