default or selected kernelversion does not have config value CONFIG_JFFS_FS.
Result is shown for kernelversion 5.15.113

Journalling Flash File System (JFFS) support

modulename: jffs.ko

configname: CONFIG_JFFS_FS

Linux Kernel Configuration
└─>File systems
└─>Miscellaneous filesystems
└─>Journalling Flash File System (JFFS) support
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
JFFS is the Journalling Flash File System developed by Axis
Communications in Sweden, aimed at providing a crash/powerdown-safe
file system for disk-less embedded devices. Further information is
available at (<http://developer.axis.com/software/jffs/>).

NOTE: This filesystem is deprecated and is scheduled for removal in
2.6.21. See
source code:
depends
CONFIG_BLOCK
CONFIG_BROKEN
CONFIG_MTD