CONFIG_ARCH_IXDP2800 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_ARCH_IXDP2800.
Result is shown for kernelversion 6.2.5

Support Intel IXDP2800

modulename: ixdp2800.ko

configname: CONFIG_ARCH_IXDP2800

Linux Kernel Configuration
└─>Intel IXP2400/2800 Implementation Options
└─>Support Intel IXDP2800
In linux kernel since version 2.6.12  
Say 'Y' here if you want your kernel to support the Intel
IXDP2800 reference platform. For more information on
this platform, see Documentation/arm/IXP2000.

source code: