default or selected kernelversion does not have config value CONFIG_DM_MQ_DEFAULT.
Result is shown for kernelversion 6.9.9

request-based DM: use blk-mq I/O path by default

configname: CONFIG_DM_MQ_DEFAULT

Linux Kernel Configuration
└─>Device Drivers
└─>Multiple devices driver support (RAID and LVM)
└─>request-based DM: use blk-mq I/O path by default
In linux kernel since version 4.1 (release Date: 2015-06-21)  
This option enables the blk-mq based I/O path for request-based
DM devices by default. With the option the dm_mod.use_blk_mq
module/boot option defaults to Y, without it to N, but it can
still be overriden either way.

If unsure say N.