CONFIG_ARCH_IXDP2801 is not available for the default architecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_ARCH_IXDP2801.
Result is shown for kernelversion 5.6.17

Support Intel IXDP2801 and IXDP28x5

configname: CONFIG_ARCH_IXDP2801

Linux Kernel Configuration
└─> Intel IXP2400/2800 Implementation Options
└─> Support Intel IXDP2801 and IXDP28x5

Say 'Y' here if you want your kernel to support the Intel
IXDP2801/2805/2855 reference platforms. For more information on
this platform, see Documentation/arm/IXP2000.