Man pages matching name qwtknob in section 3:

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