Iptables and kernel modules

Hi, I am getting the following error with ip6tables:

ip6tables-restore v1.8.7 (legacy): Couldn't load target `REJECT':No such file or directory

The kernel is compiled with CONFIG_NF_REJECT_IPV4=y but for IPv6 it is configured as a module:

# gunzip -c /proc/config.gz | grep CONFIG_NF_REJECT
CONFIG_NF_REJECT_IPV4=y
CONFIG_NF_REJECT_IPV6=m

I compiled the modules for 5.12.2 to match the kernel version, but alas, I got the error nf_reject_ipv6: disagrees about version of symbol module_layout. Further investigation revealed that I would also need the kernel’s Module.symvers.

Is there any way CONFIG_NF_REJECT_IPV6=y could be added to the kernel? Even better would be the option to mount kernel modules as a volume inside machines.