Add ipv6.disable=1 to /boot/cmdline.txt

cat /etc/modprobe.d/ipv6.conf

Don’t load ipv6 by default

alias net-pf-10 off

uncommented

alias ipv6 off

added

options ipv6 disable_ipv6=1

this is needed for not loading ipv6 driver

blacklist ipv6

https://www.raspberrypi.org/forums/viewtopic.php?t=138899