default or selected kernelversion does not have config value CONFIG_IP_NF_H323.
Result is shown for kernelversion 5.15.113

H.323 protocol support (EXPERIMENTAL)

modulename: ip_conntrack_h323.ko

configname: CONFIG_IP_NF_H323

Linux Kernel Configuration
└─>Networking options
└─>Network packet filtering (replaces ipchains)
└─>IP: Netfilter Configuration
└─>H.323 protocol support (EXPERIMENTAL)
In linux kernel since version 2.6.17 (release Date: 2006-06-17)  
H.323 is a VoIP signalling protocol from ITU-T. As one of the most
important VoIP protocols, it is widely used by voice hardware and
software including voice gateways, IP phones, Netmeeting, OpenPhone,
Gnomemeeting, etc.

With this module you can support H.323 on a connection tracking/NAT

This module supports RAS, Fast Start, H.245 Tunnelling, Call
Forwarding, RTP/RTCP and T.120 based audio, video, fax, chat,
whiteboard, file transfer, etc. For more information, please

If you want to compile it as a module, say 'M' here and read Documentation/modules.txt. If unsure, say 'N'.

source code: