How to strip the IPv6 stuff to make room in a tiny device?

│ │
│ Enables IPv6 support in kernel (builtin) and packages. │
│ │
│ │
│ Symbol: IPV6 [=n] │
│ Type : boolean │
│ Prompt: Enable IPv6 support in packages │
│ Location: │
│ -> Global build settings

That CONFIG_IPV6 switch is in the kernel configuration.
That wouldn't stop the IPv6 packages to be pulled in, anyway.
Disabling IPv6 in the kernel would save some room, indeed.
But the trick is clearly in the package dependencies: those should be modified.

No this is wrong.
Some Makefiles make uses of the switch.

find . -type f -name Makefile -exec grep "CONFIG_IPV6" '{}' ; -print

When i start a new config, select my target, disable the ipv6 config in global config,
save the config, make defconfig and go trough my config file i cant find any ipv6 packages there.
Except uhdpcd.

I tried with

make image PROFILE=tl-mr3020-v1 CONFIG_IPV6=n\
  PACKAGES="uhttpd uhttpd-mod-ubus libiwinfo-lua libc luci-base luci-app-firewall libustream-mbedtls px5g luci-mod-admin-full luci-theme-bootstrap luci-app-commands -luci-app-watchcat -watchcat -ppp -ppp-mod-pppoe -luci-proto-ppp -luci-proto-ipv6 -ip6tables -odhcp6c -kmod-ipv6 -kmod-ip6tables -libip6tc

I finally got rid of luci-proto-ipv6 but am still getting libip6tc pulled in.

Again, I think this is a dependency issue:

root@LEDE:~# opkg remove libip6tc
No packages removed.
Collected errors:
 * print_dependents_warning: Package libip6tc is depended upon by packages:
 * print_dependents_warning:    firewall
 * print_dependents_warning:    iptables
 * print_dependents_warning: These might cease to work if package libip6tc is removed.

 * print_dependents_warning: Force removal of this package with --force-depends.
 * print_dependents_warning: Force removal of this package and its dependents
 * print_dependents_warning: with --force-removal-of-dependent-packages.

Thats strange.
On my build system libip6tc doesn't have such dependencies.

Do you use latest git source or a tagged release?

I downaloaded the ImageBuilder from here and I'd say it's an official stable release.
I wouldn't use git unless there's some strong reason, like bleeding edge features I need or a big bug fixed.