default or selected kernelversion does not have config value CONFIG_NF_NAT_PROTO_GRE.
Result is shown for kernelversion 6.9.9
CONFIG_NF_NAT_PROTO_GRE (not configurable)
modulename: nf_nat_proto_gre.ko
configname: CONFIG_NF_NAT_PROTO_GRE
Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>Network packet filtering framework (Netfilter)
└─>IP: Netfilter Configuration
└─>NF_NAT_PROTO_GRE