Man pages matching name user.conf.d in section 5:

user.conf.d.5.de	debian 10 / manpages-de
user.conf.d.5.en	debian 10 / systemd
user.conf.d.5.de	debian 11 / manpages-de
user.conf.d.5.en	debian 11 / systemd
user.conf.d.5.de	debian 12 / manpages-de
user.conf.d.5.en	debian 12 / systemd