Man pages matching name systemd-firstboot in section 1:

systemd-firstboot.1.zh_CN	debian 10 / manpages-zh
systemd-firstboot.1.zh_TW	debian 10 / manpages-zh
systemd-firstboot.1.zh_CN	debian 11 / manpages-zh
systemd-firstboot.1.zh_TW	debian 11 / manpages-zh
systemd-firstboot.1.de	debian 12 / manpages-de
systemd-firstboot.1.zh_CN	debian 12 / manpages-zh
systemd-firstboot.1.zh_TW	debian 12 / manpages-zh
systemd-firstboot.1.en	debian 12 / systemd