Man pages matching name qwtrichtextengine in section 3:

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