Man pages matching name mount_namespaces in section 7:

mount_namespaces.7.en	debian 10 / manpages
mount_namespaces.7.en	debian 11 / manpages
mount_namespaces.7.en	debian 12 / manpages
mount_namespaces.7.de	debian 12 / manpages-de
mount_namespaces.7.en	debian 13 / manpages
mount_namespaces.7.de	debian 13 / manpages-de
mount_namespaces.7.fr	debian 13 / manpages-fr
mount_namespaces.7.sv	debian 13 / manpages-sv