kernelconfig_penguin
default or selected kernelversion does not have config value CONFIG_NFT_SET_RBTREE.
Result is shown for kernelversion 6.6.1

Netfilter nf_tables rbtree set module

modulename: nft_set_rbtree.ko
configname: CONFIG_NFT_SET_RBTREE

Linux Kernel Configuration
└─> Networking support
└─> Networking options
└─> Network packet filtering framework (Netfilter)
└─> Core Netfilter Configuration
└─> Netfilter nf_tables rbtree set module

In linux kernel since version 4.1 (release Date: 2015-06-21)  

This option adds the "rbtree" set type (Red Black tree) that is used
to build interval-based sets.


source code:


net/netfilter/nft_set_rbtree.c