Man pages matching name qwtplotgrid in section 3:

QwtPlotGrid.3.en	debian 10 / libqwt-doc
QwtPlotGrid.3.en	debian 10 / libqwt5-doc
QwtPlotGrid.3.en	debian 11 / libqwt-doc
QwtPlotGrid.3.en	debian 12 / libqwt-doc