CONFIG_USER_ABI_DEFAULT is not available for thedefaultarchitecture x86.
Result is shown for architecture xtensa

Default ABI only

configname: CONFIG_USER_ABI_DEFAULT

Userspace ABI
└─>Default ABI only
In linux kernel since version 5.1 (release Date: 2019-05-05)  
Assume default userspace ABI. For XEA2 cores it is windowed ABI.
call0 ABI binaries may be run on such kernel, but signal delivery
will not work correctly for them.