Several ipv6_ modules are missing from the RPI kernel in the distro

Start by inspecting the Raspberry Pi kernel build configuration for the modules listed under /lib/modules//kernel/net/ipv6 and /lib/modules//kernel/net/ipv6/netfilter, using the reported 5.4.51-v7l+ build as context. Compare the available modules with the expected IPv6 options and verify that ip6gre can load and create an IPv6 GRE tunnel. Done means the listed modules are present in the distro kernel and the reported functionality works.

Is this the right place for my bug report?
Putting it here based on feedback from XECDesign in https://github.com/RPi-Distro/repo/issues/229

Describe the bug
The following modules are missing from the RPI kernel in the Raspberry PI OS distribution, but are present in every other Linux distribution I examined (Fedora, Debian, Ubuntu, VyOS).
/lib/modules//kernel/net/

From .../ipv6:
esp6_offload.ko
fou6.ko
ila/ila.ko
ip6_gre.ko
ip6_vti.ko

And from .../ipv6/netfilter:
ip6table_security.ko
ip6t_srh.ko
ip6t_SYNPROXY.ko

To reproduce
cd /lib/modules/<kernel_version>/kernel/net/ipv6
ls

Expected behaviour
Expect the modules to be present. They are necessary to support various IPv6 functionality, such as GRE tunnels using IPv6 transport.

Actual behaviour
Some modules are present, but the ones above are missing.

System
Copy and paste the results of the raspinfo command in to this section. Alternatively, copy and paste a pastebin link, or add answers to the following questions:

• Which model of Raspberry Pi? e.g. Pi3B+, PiZeroW -- I noticed this on a Pi4, but all models are equally affected.
• Which OS and version (cat /etc/rpi-issue)? -- Included below, but all are likely affected

Raspberry Pi reference 2020-05-27
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 825107f04027269db77426046f5085475b1ee22f, stage5

• Which firmware version (vcgencmd version)? -- Included below, but all are affected identically (kernel module choices)

Sep 2 2020 21:13;13
Copyright (c) 2012 Broadcom
version 4439d2aaa6c376a2d1ef4402f142e1cf4de37c43 (clean) (release) (start)

• Which kernel version (uname -a)?

Linux 5.4.51-v7l+ #2 SMP

Logs
Not relevant... This is about kernel modules which were omitted by choice.

Additional context
I spent quite a bit of time chasing configuration issues where I thought it was a failed dependency tree trying to bring up an ip6gre tunnel on the system. systemd-networkd silently reports that it is loading the Ip6_gre module without reporting any failure to load it and all of the available debugging information makes it look like everything is fine and hints that the problem is that the GRE interface in question is coming up before the ethernet interface it depends on. Turns out that this is false and that the module not present to load is the real issue. Upon compiling a new kernel with the modules included (admittedly based on the 5.10.13 sources), everything immediately came up as expected after a reboot.