CONFIG_DEBUG_DECOMPRESS_KERNEL is not available for thedefaultarchitecture x86.
Result is shown for architecture mn10300
default or selected kernelversion does not have config value CONFIG_DEBUG_DECOMPRESS_KERNEL.
Result is shown for kernelversion 6.7-rc3

Using serial port during decompressing kernel


Linux Kernel Configuration
└─>Kernel hacking
└─>Using serial port during decompressing kernel
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
If you say Y here you will confirm the start and the end of
decompressing Linux seeing "Uncompressing Linux... " and
"Ok, booting the kernel.\n" on console.