default or selected kernelversion does not have config value CONFIG_DMAR_DEFAULT_ON.
Result is shown for kernelversion 6.2.5

Enable DMA Remapping Devices by default


Linux Kernel Configuration
└─>Device Drivers
└─>IOMMU Hardware Support
└─>Enable DMA Remapping Devices by default
In linux kernel since version 2.6.29 (release Date: 2009-03-23)  
Selecting this option will enable a DMAR device at boot time if
one is found. If this option is not selected, DMAR support can
be enabled by passing intel_iommu=on to the kernel.