Man pages matching name qwtplotsvgitem in section 3:

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