Man pages matching name spectrogramscreenshots in section 3:

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