CONFIG_MOMENCO_JAGUAR_ATX is not available for thedefaultarchitecture x86.
Result is shown for architecture mips
default or selected kernelversion does not have config value CONFIG_MOMENCO_JAGUAR_ATX.
Result is shown for kernelversion 5.4.123

Support for Momentum Jaguar board

modulename: fixup-jaguar.ko

configname: CONFIG_MOMENCO_JAGUAR_ATX

Linux/MIPS Kernel Configuration
└─>Machine selection
└─>Support for Momentum Jaguar board
In linux kernel since version 2.6.12  
The Jaguar ATX is a MIPS-based Single Board Computer (SBC) made by
Momentum Computer <http://www.momenco.com/>.

source code:
arch/mips/pci/fixup-jaguar.c

is selected by
CONFIG_MV643XX_ETH