Change the paths where mandoc makewhatis(8)generates the manual page index caches. documentation.man.cache.enable should be enabled to allow cache generation. This list should only include the paths to manpages installed in the system configuration, i. e. /run/current-system/sw/share/man. makewhatis(8) creates a database in each directory using the files mansection/[arch/]title.section and catsection/[arch/]title.0 in it. If a directory contains no manual pages, no database is created in that directory. This option only needs to be set manually if extra paths should be indexed or documentation.man.manPath contains paths that can’t be indexed.

config.documentation.man.mandoc.manPath

[ "share/man" "share/man/fr" ]