default or selected kernelversion does not have config value CONFIG_MHP_DEFAULT_ONLINE_TYPE_ONLINE_AUTO.
Result is shown for kernelversion 6.6.78

auto

configname: CONFIG_MHP_DEFAULT_ONLINE_TYPE_ONLINE_AUTO

Memory Hotplug Default Online Type
└─>auto
In linux kernel since version 6.6.78 (release Date: 2025-02-17)  
Select this if you want the kernel to automatically online
hotplugged memory into the zone it thinks is reasonable.
This memory may be utilized for kernel data.