Man pages matching name systemd.exec in section 5:

systemd.exec.5.de	debian 10 / manpages-de
systemd.exec.5.en	debian 10 / systemd
systemd.exec.5.de	debian 11 / manpages-de
systemd.exec.5.en	debian 11 / systemd
systemd.exec.5.de	debian 12 / manpages-de
systemd.exec.5.en	debian 12 / systemd