How to disable dhcpv6-client in ubuntu?

Question

DHCP

Recently there was a problem on the server.
About 7-9 MB of traffic is generated by requests like:

16:19:32.573003 IP6 fe80::e66f:13ff:fec2:5e89.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 solicit
16:19:32.573007 IP6 fe80::e66f:13ff:fec2:5e89.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 solicit
16:19:32.573267 IP6 fe80::e66f:13ff:fec2:5e89.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 solicit
16:19:32.573282 IP6 fe80::e66f:13ff:fec2:5e89.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 solicit

With all this:

ip6tables -L
ip6tables v1.6.0: can't initialize ip6tables table `filter': Address family not supported by protocol
Perhaps ip6tables or your kernel needs to be upgraded.

sysctl.conf

# cat /etc/sysctl.conf |grep ipv6
#net.ipv6.conf.all.forwarding=1
#net.ipv6.conf.all.accept_redirects = 0
net.ipv6.conf.all.accept_source_route = 0
# Disable ipv6
net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.br0.disable_ipv6=1
net.ipv6.conf.lo.disable_ipv6=1
net.ipv6.conf.virbr0.disable_ipv6=1
net.ipv6.conf.vnet0.disable_ipv6=1
net.ipv6.conf.vnet1.disable_ipv6=1
net.ipv6.conf.vnet2.disable_ipv6=1
net.ipv6.conf.vnet3.disable_ipv6=1

grub loader

GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1"
GRUB_CMDLINE_LINUX="ipv6.disable=1"

The cards also do not have ipv6 addresses, respectively, but requests are flying.
Virtual machines are spinning on the server, I thought it was one of them, put out the interfaces, but the situation has not changed.
What could be the reason in which direction to dig?