default or selected kernelversion does not have config value CONFIG_IP_NF_TFTP.
Result is shown for kernelversion 5.4.123

TFTP protocol support

modulename: ip_conntrack_tftp.ko

configname: CONFIG_IP_NF_TFTP

Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>Network packet filtering (replaces ipchains)
└─>IP: Netfilter Configuration
└─>TFTP protocol support
In linux kernel since version 2.6.12  
TFTP connection tracking helper, this is required depending
on how restrictive your ruleset is.
If you are using a tftp client behind -j SNAT or -j MASQUERADING
you will need this.

To compile it as a module, choose M here. If unsure, say Y.

source code: