Man pages matching name ssh-keysign in section 8:

ssh-keysign.8.en	debian 10 / openssh-client
ssh-keysign.8.de	debian 11 / manpages-de
ssh-keysign.8.en	debian 11 / openssh-client
ssh-keysign.8.de	debian 12 / manpages-de
ssh-keysign.8.en	debian 12 / openssh-client